PURPOSE: To provide a compact stroke cylinder device adapted to be used as operating physical force transmitting mechanical element which increases and decreases the stroke of a cylinder or changes the direction thereof so as to coaxially transmit the operating physical force.

CONSTITUTION: A cylinder device for transmitting operating physical force is composed of a first cylinder 3 in which a piston rod 2 is retractably disposed, and a second cylinder 4 which is slidably fitted on the first cylinder 3 and through which the piston rod 2 pierces so as to be supported thereby. A first oil chamber 5 defined among the front end of the first cylinder 3, the piston rod 2 and the second cylinder 4 is communicated with a second oil chamber 6 defined between a piston 2a at the inner end of the piston rod 2 and the bottom of the first cylinder 3, through an oil passage 7 so as to constitute a closed circuit structure.