PURPOSE: To make the spring property easily adaptable to the load by mounting the other springs operatable in parallel to a spring unit comprising a spring and a hydraulic shock absorber arranged in parallel with each other, and switching this spring between the operating state and the non-operating state.

CONSTITUTION: A spring unit comprising a spring and a hydraulic shock absorber 4 mounted in parallel with each other, is installed between an upper structure 1 and a wheel guide element 2 of an automobile, and the other springs 5, 6 operatable in parallel to the spring unit, are mounted in addition to the spring 3. One ends of these springs 5, 6 are connected with the wheel guide element 2, and the other ends thereof are connected with the casings of the hydraulic cylinders 7, 8. The piston rods 9, 10 of the hydraulic cylinders 7, 8 are connected with the upper structure 1, and two working chambers partitioned by the pistons of the hydraulic cylinders 7, 8 are connected with a switch valve 15 through the conductors 11-14 so that they can be selectively communicated with a volume compensating container 34 of which a gas chamber is partitioned by a separation piston 36.