To facilitate control of the vibration amplitude and the advance/retreat position of a single rod type cylinder.

This control device comprises a hydraulic pump 15 connected to an oil pressure chamber 12 on the rod side, a first solenoid valve 17 located in an intermediate hydraulic oil pipe 18 connected to a hydraulic chamber 13 on the head side from the hydraulic chamber 12 on the rod side and controlling the feed of a hydraulic oil in the hydraulic chamber 12 on the rod side to a hydraulic chamber 13 on the head side, and a second solenoid valve 21 located in a hydraulic oil discharge pipe 19, connected to a drain tank 20 from the hydraulic oil pipe 19 running from the hydraulic chamber 13 on the head side and connected to a drain tank 20 and controlling discharge of a hydraulic oil in the hydraulic chamber 13 on the head side. The piston pressure receiving area of a hydraulic chamber 12 on the rod side and the piston receiving pressure area of the hydraulic chamber 13 on the head side are set to respective values corresponding to a load W exerted on a rod 11a so that controlled variables of the first and second solenoid valves 17 and 21 coincide with each other.