To control an attitude by the expansion/contraction operation of a shock absorber at a low pressure and to maintain the controlled attitude even after the elimination of driving force.

A spring seat 5 for seating the lower end of a suspension spring 2 wound around a shock absorber 1 is slidably fitted to an unsprung member 6 fixedly provided at the outer periphery of a shock absorber body 3, and supported to a lower end flange part 6b (a body 3) of the unsprung member 6 through a first coil spring 7 and a first expansion/contraction liquid chamber 8 in a direction opposed to the spring force of the suspension spring 2. The interior of the body 3 and the chamber 8 are communicated through a hole 52, and the interior of the body 3 is communicated with a second expansion/ contraction liquid chamber 26 of an oil pressure generating mechanism 21 through a hollow hole 4b of a piston rod 4. A second coil spring 31 is stretched in the chamber 26. When an external screw member 28 is rotated by a motor 27, the chamber 26 is expanded/contracted through an internal screw member 29 to change the volume of the chamber 8 in an opposite phase, and a body attitude can be controlled by the height change of a car through the displacement of the spring seat 5.