To provide a control cylinder having control characteristic to meet an objective.

The control cylinder 10 controls a suspension cylinder 20 connected to each of four working fluid chambers 150 by the movement of a piston assembly 72 inside a housing 70. A connection shaft 76 of the piston assembly 72 is slidably brought into contact with a partition wall part 104 via an O-ring 114. The sliding resistance is increased when a large diameter part 140 provided at the center of the connection shaft 76 is slidably brought into contact with the partition wall part 104. In other words, when the piston assembly 72 is located at the neutral position in the control cylinder 10, the piston assembly 72 is hardly moved so that control of the suspension cylinder 20 is not performed unnecessarily. Thus, the control cylinder 10 can enhance the grounding property during the traveling on a rough road while maintaining the firm traveling feeling during the traveling on a smooth road.