To provide a power transmission device in which the strength of a cam for assisting pressure contact or a back torque limiter cam can be improved while achieving weight reduction.

The power transmission device has a clutch housing 2, a clutch member 4, a pressure member 5, and a cam for assisting pressure contact or a back torque limiter cam. The power transmission device interrupts torque inputted to an input member or transmits the torque to an output member by separation or pressure contact between driving clutch plates 6 and driven clutch plates 7. The cam for assisting pressure contact or the back torque limiter cam is obtained by press-molding each of metallic members fixed to the clutch member 4 side and the pressure member 5 side respectively.