To improve responsiveness for filling new air into a combustion chamber by operatively associating first and second throttle valves with each other in a closing direction.

In a scooter type motorcycle, an engine unit 11 comprising an engine main body 12 and a rear wheel transmission gear 13 is mounted on the lower side of the bending part of a side flame 2c. The engine main body 12 is provided with a supercharger 50, air pressurized by a supercharging mechanism is supplied into a combustion chamber 65 through a pressure intake pipe 53 and an intake control valve 251. At this time, a carburetor 54 for composing a fuel supplying device N for supplying fuel before pressurizing is carried out in a crank chamber 63, an intake control valve 251 after pressurizing is arranged, and the carburetor 54 and the intake control valve 251 are operatively associated with the operation of a throttle 301. When the control valve 251 is opened in linkage with the carburetor 54, new air is filled into a combustion chamber 65 without time lag, and thereby, it is possible to improve responsiveness for supplying pressurized new air and fuel.