A compact power unit for a vehicle having a clutch actuator is provided. The power unit includes a clutch actuator and a drive force transmission mechanism for transmitting the drive force of the clutch actuator to the clutch. The clutch actuator and the drive force transmission mechanism are arranged within a casing of the power unit. A drive shaft of the clutch actuator extends in the vertical direction. The drive force transmission mechanism includes a worm shaft coupled to the drive shaft of the clutch actuator, a first solid of revolution including a worm wheel portion which engages the worm shaft, a second solid of revolution which engages a gear portion of the first solid of revolution, and a ball cam. The ball cam converts torque from the second solid of revolution into a force which acts in the axial direction of a slide shaft of the clutch.