This paper reconstructs the design process of Louis I. Kahn's Phillips Exeter Academy Library through a morphological analysis of the basic form used by the architect. The discussion sequence is as follows: 1) Analysis of chronologically ordered design sketches to induce the basic form. 2) Examination of their adaptability to the library's architectural program. 3) Discussion on the basic form, which plays an important role in controlling the relationship between program requirements and formal transformations in the design. Keywords: Louis I. Kahn, Phillips Exeter Academy Library, design process, design method, form. The Phillips Exeter Academy Library (Exeter Library), built between 1966 and 1971, is one of Kahn's most representative works. Located in Exeter, New Hampshire, it is the central library of the Phillips Exeter Academy. The campus, composed of a neoclassical architectural complex, creates an atmosphere of a prestigious East Coast school. The Exeter Library, while harmonizing with this environment, acquires a distinct character through its geometric clarity. Kahn's architectural theory is closely related to his actual design process. This paper aims to provide new insights into his architectural theory by examining his actual design process. The design sketches of the Exeter Library, which are preserved in the Louis I. Kahn Collection at the University of Pennsylvania, are a key source for understanding the design process. These sketches, along with office drawings, provide a detailed record of the design development. The design process of the Exeter Library is characterized by a series of studies, each focusing on different aspects of the design. These studies include the spatial composition, the tower, the entrance staircase, and individual spatial units. The design process is marked by a consistent form, which is maintained throughout the design. This basic form is derived from the initial sketches and is reflected in the final design. The basic form of the Exeter Library is characterized by a three-layered spatial composition, with the outer perimeter, inner perimeter, and central core. This form is closely related to the architectural program, which outlines the functional requirements of the library. The basic form is also influenced by Kahn's philosophical views on architecture, particularly his emphasis on the relationship between architecture and the human experience. The design process of the Exeter Library reflects Kahn's deep understanding of architecture as a means of creating a space that is both functional and meaningful. The library is not merely a place for storing books, but a space that invites people to engage with the books and the environment. This is achieved through the careful consideration of spatial organization, light, and materials. The final design of the Exeter Library is a testament to Kahn's ability to balance form and function, creating a space that is both aesthetically pleasing and functionally effective.This paper reconstructs the design process of Louis I. Kahn's Phillips Exeter Academy Library through a morphological analysis of the basic form used by the architect. The discussion sequence is as follows: 1) Analysis of chronologically ordered design sketches to induce the basic form. 2) Examination of their adaptability to the library's architectural program. 3) Discussion on the basic form, which plays an important role in controlling the relationship between program requirements and formal transformations in the design. Keywords: Louis I. Kahn, Phillips Exeter Academy Library, design process, design method, form. The Phillips Exeter Academy Library (Exeter Library), built between 1966 and 1971, is one of Kahn's most representative works. Located in Exeter, New Hampshire, it is the central library of the Phillips Exeter Academy. The campus, composed of a neoclassical architectural complex, creates an atmosphere of a prestigious East Coast school. The Exeter Library, while harmonizing with this environment, acquires a distinct character through its geometric clarity. Kahn's architectural theory is closely related to his actual design process. This paper aims to provide new insights into his architectural theory by examining his actual design process. The design sketches of the Exeter Library, which are preserved in the Louis I. Kahn Collection at the University of Pennsylvania, are a key source for understanding the design process. These sketches, along with office drawings, provide a detailed record of the design development. The design process of the Exeter Library is characterized by a series of studies, each focusing on different aspects of the design. These studies include the spatial composition, the tower, the entrance staircase, and individual spatial units. The design process is marked by a consistent form, which is maintained throughout the design. This basic form is derived from the initial sketches and is reflected in the final design. The basic form of the Exeter Library is characterized by a three-layered spatial composition, with the outer perimeter, inner perimeter, and central core. This form is closely related to the architectural program, which outlines the functional requirements of the library. The basic form is also influenced by Kahn's philosophical views on architecture, particularly his emphasis on the relationship between architecture and the human experience. The design process of the Exeter Library reflects Kahn's deep understanding of architecture as a means of creating a space that is both functional and meaningful. The library is not merely a place for storing books, but a space that invites people to engage with the books and the environment. This is achieved through the careful consideration of spatial organization, light, and materials. The final design of the Exeter Library is a testament to Kahn's ability to balance form and function, creating a space that is both aesthetically pleasing and functionally effective.