The invention is directed to provide a shock absorber in which hydraulic fluid is restrained from leaking out from a gap between a sub-check valve provided at a passage opening of an orifice passage and a disc valve. The sub-check valve (133) is biased toward the opening (126) of the orifice passage (130) using a biasing disc (135) (biasing member) of substantially equal diameter to the sub-check valve (133). This makes it possible to restrain hydraulic fluid in a first chamber (2A) from leaking out from a gap between a disc valve (121) and the sub-check valve (133) into a second chamber (2B) when piston velocity during an extension stroke is low (0.1 m/s or lower, exclusive zero), and thus obtain an intended damping force.