The paper explores the Josephson diode effect (JDE) in a superconductor/quantum dot (QD)/superconductor junction under the influence of a magnetic field and Rashba spin-orbit interaction (RSOI). Using the Keldysh non-equilibrium Green's function technique, the authors calculate the Josephson current in the QD junction. They find that JDE is induced in the chiral QD junction with a large rectification coefficient (RC) when RSOI and an external magnetic field are present simultaneously. The sign and magnitude of the RC are highly controllable by the magnetic field and RSOI. For realistic RSOI strength and magnetic field, the RC can be tuned to as high as 70% by an external gate potential, indicating a significant JDE in the QD junction. The proposed QD-based Josephson diode (JD) may serve as a potential component in superconducting devices. The study highlights the importance of RSOI in enhancing the JDE and the tunability of the RC through external gate voltage.The paper explores the Josephson diode effect (JDE) in a superconductor/quantum dot (QD)/superconductor junction under the influence of a magnetic field and Rashba spin-orbit interaction (RSOI). Using the Keldysh non-equilibrium Green's function technique, the authors calculate the Josephson current in the QD junction. They find that JDE is induced in the chiral QD junction with a large rectification coefficient (RC) when RSOI and an external magnetic field are present simultaneously. The sign and magnitude of the RC are highly controllable by the magnetic field and RSOI. For realistic RSOI strength and magnetic field, the RC can be tuned to as high as 70% by an external gate potential, indicating a significant JDE in the QD junction. The proposed QD-based Josephson diode (JD) may serve as a potential component in superconducting devices. The study highlights the importance of RSOI in enhancing the JDE and the tunability of the RC through external gate voltage.