PURPOSE: To lessen the variation of a body height and the inclination of the body during travel on a rugged road and also improve the operator's riding comfortableness.

CONSTITUTION: The central parts of longitudinal members 11 fitting wheels are supported by supporting mechanisms 12 so as to be vertically movable, at both right and left side faces of a vehicle body 10 respectively. And the front wheels 13 and the rear wheels 14 are provided near the front and rear ends of the longitudinal members 11 fitting these wheels and the vehicle body 10 and the right and left longitudinal members 11 fitting the wheels are connected to each other by right and left suspension cylinders 17 respectively. These right and left suspension cylinders 17 are connected to each other through a changeover valve 34 so as to change over the state that these cylinders oppositely extend or contract and the state that these have independently the suspension function.