In a cylinder apparatus in the form of a shock absorber, a spring seat is mounted within a cylinder, and clearance-fitted to a piston rod with a first lateral clearance for moving along the piston rod longitudinally of the cylinder. The spring seat includes a longitudinal extension at one longitudinal end for defining a space between the longitudinal extension and the piston rod. A rebound spring is mounted around the piston rod within the cylinder. The rebound spring has one longitudinal end fixed to another longitudinal end of the spring seat. An elastic member is retained in the defined space by the longitudinal extension of the spring seat, and clearance-fitted to the piston rod with a second lateral clearance for moving along the piston rod longitudinally of the cylinder, wherein the second lateral clearance is smaller than the first lateral clearance.