Solving Means: A body frame (2) is composed of a front frame (22) and a rear frame (23) connected to each other. The rear frame (23) is formed by die-cast of aluminum and split into a left part (23L) and a right part (23R), and a battery box (16) for accommodating a battery is provided between the two parts. An assist unit (1) is suspended on the rear frame (23). A hanger portion (70b) of the assist unit is disposed between bosses (25BR and 25BL) and fastened together to the rear frame (23). <IMAGE>
