Provided is a power unit for a vehicle including an engine main body of an engine having: a valve system capable of changing operational modes of each engine valve; valve controlling apparatuses for controlling operations of the valve system; and a crankcase housing a transmission, the engine main body being mounted on a vehicle frame. The power unit for a vehicle achieves reduction in size of the engine main body in a direction along the axis of a cylinder, and increases the freedom of arranging parts designed to be placed on an upper end portion of the engine main body. The valve controlling apparatuses are attached to the top surface of the crankcase.