Abstract: A power transmission device includes a pulley (4) and a hub (11) that are arranged on the same rotation axis, and a connecting member (13) that connects these rotation bodies. The power transmission device includes a first connecting structure (14) that connects one end portion (13a) of the connecting member to the pulley so that one end portion (13a) cannot be separated, and a second connecting structure (15) that connects the other end portion (13b) of the connecting member to the hub so that the other end portion (13b) can be separated. The second connecting structure includes a columnar body (21) that extends through the other end portion (13b) of the connecting member (13) in the axial direction, a head portion (28) that is provided on the columnar body (21), a slit (22) of the connecting member (13), and a belleville spring (29) that presses the connecting member (13) against the rotation body.