To provide an adjusting device for enabling reduction in machining cost.

The adjusting device C which is provided with a cylinder 1 making one end 1a face outside a shock absorber S and projecting the other end 1b inside the shock absorber S, and an adjustment rod 2 inserted into the cylinder so as to be freely movable in an axial direction and which adjusts damping force produced in a variable damping valve 15 contained in a passage 14 for communicating between one chamber 12 and the other chamber 13 provided inside the shock absorber S through the axial movement with respect to the cylinder of the adjustment rod 2, is equipped with a nut member 3 which is formed into a cylindrical shape movably inserted in an axial direction in a state of being detent around a shaft and which contains a female screw 3a in an inner periphery and an operation member containing a male screw 4a screwed into the nut member 3 and an operation part 4b projected to the outside from the mail screw 4a screwed into the nut member 3 and one end 1a to be allowed to rotate through external operation. The nut member 3 is moved in an axial direction by the rotation of the operation member 4 to transmit the movement of the nut member 3 to the adjustment rod 2.