To easily and surely hold and release a resting state of a piston in a hydraulic cylinder, in a simple constitution.

This hydraulic cylinder resting device includes a hook part 2 extending in the moving direction of a piston 103b from the tip of the piston 103b of the hydraulic cylinder 103 and having an outward projected projection 2a crossing with the moving direction, a hook receiving part 3 movable to a resting position for abutting on the projection 2a of the hook part 2 moving in response to the movement of the piston 103b or a release position for allowing the movement of the projection 2a of the hook part 2 in response to the movement of the piston 103b, and an operation part 4 for moving the hook receiving part 3 by manual operation from an external part of the hydraulic cylinder 103. In the form wherein the piston 103b is moved to a position for contractively operating a piston rod 103c, the piston 103b is held in a resting state by moving the hook receiving part 3 to the resting position through the manual operation of the operation part 4. While, the resting state is released by moving the hook receiving part 3 to the release position by through manual operation of the operation part 4.