PURPOSE: To prevent the oscillation of an axle at the curve traveling time and the floating of wheels at the time of traveling on an uneven road by forming air suspension structure by the combination of both front and rear brackets, front and rear interposing members, a torque rod, an air spring, and the like.

CONSTITUTION: Air suspension structure is interposed between a body frame 1 and an axle 3. At the time of normal travel, a torque rod 9, the axle 3 and a plate spring 8 forming the air suspension structure are vertically moved in this order following the vertical movement of the body frame 1. At this time, the plate spring 8 is brought into contact, at its front end, with a front upper stopper 13 and held onto the reference height level by an air spring 10, but the rear end is not brought into contact with a rear upper stopper 15. At the curve traveling time, both front and rear ends of the plate spring 8 are respectively brought into contact with the contact plates 17 of both front and rear brackets 6, 7 so as to prevent the laterally outward oscillation of the axle 3.