PURPOSE: To prevent bounding of body by regulating excess pitching of a slide rail by fitting a control rod which is allowed to telescopically move only predetermined amount between a vehicle frame near a link mechanism and the slide rail.

CONSTITUTION: A pair of right and left control rods 45, is slantingly fitted along the longitudinal direction of a body between the rear portion of a vehicular body frame 2 near a link mechanism 19 and a slide rail 11. With regard to the control rod 45, one end of a rod 46 as a portion of the same rod 45 is fastened to a shaft 33 fixed on the body frame 2, and the other end of the rod 46 is slidably inserted to a cylindrical guide member 47 connected to a side rail 11, and further stoppers are mounted on a part of the rod 46 where a guide element 47 is interposed between the stoppers. The control rod 45 can move telescopically only within a gap between the stoppers and guide element 47. Then, even when a snowmobile passes over gradual undurations and local projections formed on a snow surface, the slide rail 11 optimally pitches within an expansion and contraction range of the control rod 45, allowing the track belt 13 to secure earthing.