PURPOSE: To improve riding comfort of a vehicle by preventing damping force from rising rapidly when the traveling speed of a piston is high.

CONSTITUTION: An oil passage 32 which communicates a reservoir chamber C with a rod side oil chamber A is formed in a rod guide 31 positioned on the upper side of an inner cylinder 4 and an outer cylinder 1, and on the way to the oil passage 32, disc valves 34, 34 which generate damping force are mounted. It is thus possible to improve riding comfort of the vehicle by restraining the damping force from increasing rapidly for making the wheels follow the roughness of a road positively in the elongation process of the piston rod 9 when the traveling speed of a piston is in a high speed range.