To improve a shock absorber capable of adjusting a damping force while pressing the inner periphery side of a leaf valve.

A shock absorber D includes a piston 1 which is partitioned into one chamber A and the other chamber B, a pressure side flow path 11 which is formed in the piston 1 and makes one chamber A communicate with the other chamber B, an annular plate-like leaf valve 21 which blocks an outlet of the pressure side flow path 11 so as to be openable and closable while being laminated at the one-chamber side of the piston 1, a piston rod 3 which stands up at the one-chamber side of the piston 1, and an energizing spring 4 which energizes the leaf valve 21 to the piston side, and also includes a jack chamber J1, a jack member 5 which can be separated from and approximate the leaf valve 21 accompanied by the expansion and contraction of the jack chamber J1 while one end of which contacts with the energizing spring 4, a flow path J2 for a jack which always communicates with the jack chamber J1 while being formed at a piston rod 3, and an adjuster 7 which supplies and discharges fluid for the jack to the jack chamber J1 through the flow path J2 for the jack while being attached to the piston opposite side of the piston rod 3.