This supercharger for a motorcycle is driven by power of a crankshaft of a combustion engine, and compresses intake air to be supplied to the combustion engine. The supercharger has an impeller of a centrifugal type, and an intake air control valve is disposed on the upstream side of the impeller of the supercharger with respect to a flow direction of the intake air. The intake air control valve is disposed so as to face a suction port of the supercharger in the flow direction of the intake air. The intake air control valve adjusts the amount of the intake air flowing into the impeller, and in addition, provides a preswirl to the intake air flowing into the impeller.