In an internal combustion engine for a saddle riding vehicle, in which a gear transmission and a shift drum of a shift change device is stored in a crankcase, the gear transmission having a plurality of transmission shafts parallel to a crankshaft extending in a vehicle width direction, a single pump shaft common to first and second oil pumps is rotatably supported by the crankcase. First oil pump rotors of the first oil pump are disposed at a mating face of a pair of left and right crankcase half bodies. A second oil pump rotor of the second oil pump is disposed between a pump gear and the first oil pump and at a side surface, on a side opposite to the mating face, of one crankcase half body out of the pair of left and right crankcase half bodies, the pump gear being arranged in the pump shaft.