In this paper, by adding graphene to the platinum silicide (PtSi) photodetector and using the photogating effect, the responsivity is significantly improved in the PtSi photodetector. In this photodetector, the PtSi layer detects the light, and the graphene increases the responsivity with the photogating effect. The responsivity of the PtSi photodetector with graphene is 1.5 A/W in the optical power of 13.6 µW. The responsivity in the PtSi photodetector with graphene and without graphene is compared. By adding graphene to the PtSi photodetector, the responsivity is much improved compared to the conventional PtSi photodetector.