A shock absorber (D, D1) comprising: a cylinder (1, 21); a piston (2, 22) slidably inserted into the cylinder (1, 21) to partition the inside of the cylinder (1, 21) into an expansion-side chamber (R1, R4) and a contraction-side chamber (R2, R5); a piston rod (4, 23) movably inserted into the cylinder (1, 21) and provided with one end connected to the piston (2, 22); a damping passage (3a, 3b, 31) that connects the expansion-side chamber (R1, R4) with the contraction-side chamber (R2, R5); a compression chamber (R3, R6); a free piston (9, 29) movably inserted into the compression chamber (R3, R6) to partition the compression chamber (R3, R6) into an expansion-side compression chamber (7, 27) and a contraction-side compression chamber (8, 28); an expansion-side flow passage (5, 25) that connects the expansion-side chamber (R1, R4) with the expansion-side compression chamber (7, 27); a contraction-side flow passage (6, 26) that connects the contraction-side chamber (R2, R5) with the contraction-side compression chamber (8, 28); an expansion-side bypass valve (15, 32) arranged closer to the expansion-side chamber (R1, R4) side relative to the piston (2, 22) and provided in the expansion-side flow passage (5, 25), the expansion-side bypass valve (15, 32) being configured to admit only a flow directed from the expansion-side chamber (R1, R4) to the expansion-side compression chamber (7, 27) and generate resistance; a contraction-side bypass valve (16, 33) arranged closer to the expansion-side chamber (R1, R4) side relative to the piston (2, 22) and provided in the expansion-side flow passage (5, 25) in parallel with the expansion-side bypass valve (15, 32), the contraction-side bypass valve (16, 33) being configured to admit only a flow directed from the expansion-side compression chamber (7, 27) to the expansion-side chamber (R1, R4) and generate resistance; an expansion-side elastic stopper (17, 44) configured to stop the free piston (9, 29) at an expansion-side stroke end; and a contraction-side elastic stopper (18, 45) configured to stop the free piston (9, 29) at a contraction-side stroke end, characterized by a spring member (10, 42, 43) configured to generate a biasing force for suppressing displacement of the free piston (9, 29) with respect to the compression chamber (R3, R6); and a bypass valve disc mounted closer to the expansion-side chamber (R1, R4) side of the piston rod (4, 23) relative to the piston (2, 22) and included in a part of the expansion-side flow passage (5, 25) connected to the expansion-side chamber (R1, R4), wherein the expansion-side bypass valve (15, 32) and the contraction-side bypass valve (16, 33) are leaf valves mounted to the bypass valve disc. a cylinder (1, 21); a piston (2, 22) slidably inserted into the cylinder (1, 21) to partition the inside of the cylinder (1, 21) into an expansion-side chamber (R1, R4) and a contraction-side chamber (R2, R5); a piston rod (4, 23) movably inserted into the cylinder (1, 21) and provided with one end connected to the piston (2, 22); a damping passage (3a, 3b, 31) that connects the expansion-side chamber (R1, R4) with the contraction-side chamber (R2, R5); a compression chamber (R3, R6); a free piston (9, 29) movably inserted into the compression chamber (R3, R6) to partition the compression chamber (R3, R6) into an expansion-side compression chamber (7, 27) and a contraction-side compression chamber (8, 28); an expansion-side flow passage (5, 25) that connects the expansion-side chamber (R1, R4) with the expansion-side compression chamber (7, 27); a contraction-side flow passage (6, 26) that connects the contraction-side chamber (R2, R5) with the contraction-side compression chamber (8, 28); an expansion-side bypass valve (15, 32) arranged closer to the expansion-side chamber (R1, R4) side relative to the piston (2, 22) and provided in the expansion-side flow passage (5, 25), the expansion-side bypass valve (15, 32) being configured to admit only a flow directed from the expansion-side chamber (R1, R4) to the expansion-side compression chamber (7, 27) and generate resistance; a contraction-side bypass valve (16, 33) arranged closer to the expansion-side chamber (R1, R4) side relative to the piston (2, 22) and provided in the expansion-side flow passage (5, 25) in parallel with the expansion-side bypass valve (15, 32), the contraction-side bypass valve (16, 33) being configured to admit only a flow directed from the expansion-side compression chamber (7, 27) to the expansion-side chamber (R1, R4) and generate resistance; an expansion-side elastic stopper (17, 44) configured to stop the free piston (9, 29) at an expansion-side stroke end; and a contraction-side elastic stopper (18, 45) configured to stop the free piston (9, 29) at a contraction-side stroke end, characterized by a spring member (10, 42, 43) configured to generate a biasing force for suppressing displacement of the free piston (9, 29) with respect to the compression chamber (R3, R6); and a bypass valve disc mounted closer to the expansion-side chamber (R1, R4) side of the piston rod (4, 23) relative to the piston (2, 22) and included in a part of the expansion-side flow passage (5, 25) connected to the expansion-side chamber (R1, R4), wherein the expansion-side bypass valve (15, 32) and the contraction-side bypass valve (16, 33) are leaf valves mounted to the bypass valve disc.