A combustion engine (E) mounted on a motorcycle includes an engine rotary shaft (39) extending in a vehicle widthwise direction and a supercharger (62) disposed rearwardly of a cylinder block (42). The combustion engine (E) also includes an air intake duct (70) through which an incoming wind (A) flowing forwardly of a traveling direction with respect to the combustion engine (E) is introduced into the supercharger (62). The air intake duct (70) is fluid connected with an air intake port of the supercharger (62) after having passed laterally of the combustion engine (E).