A motorcycle is generally provided with a lateral pair of frame bodies, a pivot shaft connected between the frame bodies, a swing arm mechanism supported to the pivot shaft to be swingable and adapted to support a rear wheel. A housing box for accommodating articles is disposed below a seat, and the housing box is composed of an upper portion and a lower extension portion which extends vertically downward so as to pass through a space of the swing arm mechanism between the pivot shaft and the rear wheel in an installed state of the motorcycle.