A cam device having a drive cam and a driven cam; and a friction engagement device having at least one friction plate and at least one separation plate are provided. The friction engagement device is configured so as to be put into a connected state by pressing the friction plate and the separation plate against each other by the driven cam, and a disconnected state. Also provided are a rotation transmission state switching device having a first member and a second member coaxially arranged, and a mode selecting part configured to rotate or displace in the axial direction according to rotation of the drive cam. The rotation transmission state switching device has at least one mode of a free mode and a lock mode of the first member and the second member, and a one-way clutch mode.