This paper investigates the speed of scalar-induced gravitational waves (SIGWs) using data from the European Pulsar Timing Array (EPTA) DR2, Parkes Pulsar Timing Array (PPTA) DR3, and the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 15-year data set. The study aims to determine the speed of SIGWs, which are hypothesized to originate from scalar perturbations during inflation. The analysis employs a Bayesian approach to constrain the speed of SIGWs, finding that it must be greater than 0.61 at a 95% credible interval to be consistent with pulsar timing array observations. This result aligns with the prediction of general relativity that the speed of gravitational waves is equal to the speed of light (c_g = 1) within a 90% credible interval. The findings highlight the potential of pulsar timing arrays as a powerful tool for probing the speed of SIGWs, which could provide insights into the early universe and new physics beyond the standard model. The study also discusses the implications of these results for our understanding of gravity and the fundamental laws of the universe.This paper investigates the speed of scalar-induced gravitational waves (SIGWs) using data from the European Pulsar Timing Array (EPTA) DR2, Parkes Pulsar Timing Array (PPTA) DR3, and the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 15-year data set. The study aims to determine the speed of SIGWs, which are hypothesized to originate from scalar perturbations during inflation. The analysis employs a Bayesian approach to constrain the speed of SIGWs, finding that it must be greater than 0.61 at a 95% credible interval to be consistent with pulsar timing array observations. This result aligns with the prediction of general relativity that the speed of gravitational waves is equal to the speed of light (c_g = 1) within a 90% credible interval. The findings highlight the potential of pulsar timing arrays as a powerful tool for probing the speed of SIGWs, which could provide insights into the early universe and new physics beyond the standard model. The study also discusses the implications of these results for our understanding of gravity and the fundamental laws of the universe.