PURPOSE: To increase the number of stages where the damping force can be varied by providing a rotary valve in a hollow part of a piston cylindrical member, a side hole piercing a cylindrical member or one of side walls of the valve, orifices of different sectional area which penetrate the other side wall, and a communicating passage.

CONSTITUTION: Two flow passages, i.e., an expansion side flow passage D which passes a through hole 2a in the expansion stroke and opens an expansion side damping valve 9 to reach a lower chamber B, and an expansion side bypass flow passage E which passes from ports 3c, 3d, 3e, 3f through one of five orifices 12a, 12b, 12c, 12d, 12e, through a hollow part 1 2f and a through hole 3b, and through a constant orifice 16a and reaches the lower chamber B are provided between the upper and lower chambers A, B. At the same time, two flow passages of a compression side flow passage F on the compression stroke, and a compression side bypass flow passage G are provided. The throttling opening of the expansion and compression side bypass flow passages E, G can be switched to six stages including the full-open and the full-close stages by turning a rotary valve 12. Thus, the characteristic of the generated damping force can be switched to six stages.