To facilitate assembly of a push cylinder device on a small-sized transmission case by miniaturizing the push cylinder device.

The block structure of the push cylinder has a plurality of push cylinders 117, 118 and a selector valve for switching the oil feed direction to the push cylinders 117, 118 on a single block forming a cylinder body 115. The selector valve is made into a rotary spool 116 having a switching groove 116a on a part of a peripheral surface thereof and is structured to expand and contract the push cylinders 117, 118 by rotation of the rotary spool 116. By the rotation of the rotary spool 116, the push cylinders 117, 118 are expanded and contracted, and a throttle amount of a variable throttle that varies the expansion/contraction speeds of the push cylinders 117, 118 is changed concurrently.