POWER TRANSMISSION DEVICE

A power transmission device has a first pressure member (), a second pressure member () and a back-torque transmitting cam. The first pressure member () presses the drive-side clutch plates () and the driven-side clutch plates () against each other. The second pressure member () releases a press-contact force between the drive-side clutch plates () and the driven-side clutch plates (). The back-torque transmitting cam moves the second pressure member () relative to the first pressure member () to keep pressing the drive-side clutch plates () and the driven-side clutch plates () against each other when a rotational force is input to the clutch member (), via the output shaft (), in a process where the weight member () moves from the radially-outer position to the radially-inner position and the first pressure member () moves to follow the interlocking member ().