PURPOSE: To secure a larger storage space by disposing a storage box between a seat and a unit swing type engine, inclining a cylinder of an engine body forward, and disposing an air cleaner in front of a transmission case.

CONSTITUTION: A unit swing type engine 7 of a scooter type vehicle is composed of an engine body 11, power transmission mechanism provided with a V-belt or the like for transmitting the power of the engine body 11 backward, and a transmission case 12 accommodating the power transmission mechanism and supporting a rear wheel 8. The engine body 11 is arranged with its cylinder inclining forward in a nearly horizontal direction, and an air cleaner 21 is disposed at the side of this cylinder and in front of the transmission case 12. A storage box 32 with an almost elliptic upper opening is disposed in space formed between the engine 7 and a seat 3 and surrounded by a body cover 31, and supported to a body frame 5 by support legs 33, 34.