A power transmission apparatus comprises an input shaft, an output shaft, a clutch device, and an actuator. The clutch device comprises a clutch hub, a clutch housing, a clutch pack, an input side cam mechanism for pressing the clutch pack toward the output shaft, an output side cam mechanism for pressing the clutch pack toward the input shaft, a return spring for urging the clutch pack to have its elements moved away from each other, and a drive shaft having an input side gear for transmitting the driving force of the actuator to the input side cam mechanism, and an output side gear for transmitting the driving force of the actuator to the output side cam mechanism.