PURPOSE: To lower flow resistance of working fluid and to smooth an action of a control cylinder and to compacitify a device by shortening passage length in each oil passage.

CONSTITUTION: End caps 17, 18, which close both end parts of a control cylinder 11 consisting of an internal cylinder 12 and an external cylinder 13 so as to form a fluid chamber 19 in the inside of the internal cylinder 12, are arranged, while a communication path 28, by which an upper fluid chamber 19a and a lower fluid chamber 19b divided by means of a piston 22 are connected together, is opened/closed by means of a rotary valve 29 arranged in the tip part of a piston rod 21. The end caps 17, 18 are provided with the first check valve 38 and the second check valve 44, by which working fluid inside a reservoir chamber 20 is allowed to flow only into both of the fluid chamber 19a, 19b sides via the first - the third oil passages 36, 37, 43. In addition, a communication hole 46 connecting the fluid chamber 19 and the reservoir chamber 20 to each other is arranged in an approximately center of the internal cylinder 12.