PURPOSE: To obtain a suitable and positive damping force by a simple structure by connecting an A port to a cylinder device between a car body and a wheel, connecting a B port to an accumulator, and providing a valve, or a throttle for controlling the flow of hydraulic fluid to each of a first passage to a fourth passage connecting both the ports to each other.

CONSTITUTION: When a wheel 2 is passed through the recessed part of a road surface, the piston 8 of a cylinder device 5 is lowered, and hydraulic fluid flowing into a B port of a damping force variable valve 13 is throttled by a throttle of a third passage 18 to cause the differential pressure to generate damping force. When the lowering speed of the piston is increased, the quantity of hydraulic fluid is increased, and the degree of opening of the first valve device 21 in a first passage 16 is increased with increasing the quantity of the fluid to raise damping force slowly. When the wheel 2 passes through the projected part 3b on the road surface, the piston is raised, the check valve of a fourth passage 19 permits the hydraulic fluid to flow from the A port to the B port, and thus the hydraulic fluid flows through the third, fourth passages 18, 19 to restric resctrict damping force at low levels. When the lowering speed of the piston is increased, a second valve device 22 is opened to raise damping force slowly.