To perform positioning of a cylinder with a built-in valve for positioning control with high precision, to improve durability of a seal and a bearing, and to reduce size.

A nut 2 is attached to the piston rod 1 of a hydraulic cylinder, a screw stem 3 engaged with the nut 2 is supported by a bearing 4 and fixed at an outer rotor 5. A control motor 24 is joined with an inner rotor 6 making slide contact with the outer rotor 5. Since the ends on both sides of the screw stem 3, the bearing 4, and the outer rotor 5 are always connected to a pressure chamber 9 on the cylinder press side and pressures are the same as each other and a load in one direction by a pressure is not exerted on the bearing 4, feedback of the position of the piston rod 1 is transmitted to the outer rotor 5 with high precision. Thereby, by positioning the control motor 24, the piston rod 1 is positioned with high precision.