A power transmission device for a vehicle includes a control unit adapted to automatically control engagement or disengagement of a clutch, and is further equipped with a clutch lever for manually engaging or disengaging the clutch. The power transmission device includes a manual mode in which the clutch is engaged or disengaged by a driver performing an engagement or disengagement operation with the clutch engagement/disengagement operating element and an automatic mode in which the clutch is engaged or disengaged under the control of the control unit without the driver performing the engagement or disengagement operation. The manual mode or the automatic mode is selectable by the driver. In the manual mode, it is further possible to select a plurality of control modes with differing levels of intervention of the automatic control.