In a motor generator pulley 122, a mechanical clutch 105 and a switching unit 132 are provided such that the mechanical clutch 105 is interposed between a first power transmission unit 104A and a second power transmission unit 104B and can transmit power even when an engine 102 serves as a drive element and a motor generator 103 serves as a drive element and when the motor generator 103 serves as the drive element and the engine 102 serves as the driven element, and that the switching unit 132 can switch, when at least one of the engine 102 and the motor generator 103 serves as a drive element, the mechanical clutch 105 so as to inhibit the engine 102 and the motor generator 103 from being connected to each other.