This invention pertains to a power transmission device suited for use in a hybrid car for selective transmission of its engine and motor powers. The power transmission device is used to transmit and cut off driving forces from an internal combustion engine or a motor of a hybrid car, and includes a two-way clutch having engaging elements, and a control mechanism for controlling the locking and freeing of the two-way clutch. The control mechanism includes an electromagnetic clutch having an electromagnet and an armature. By mounting such power transmission devices on the outputs of the engine and the motor, it is possible to easily transmit and cut off driving force by simply turning on and off the electromagnet.