PURPOSE: To simplify incorporating work of a relay valve by forming a movable body of the realy valve which is arranged on one of the walls of an air cylinder body by a diaphragm and a controlling body which opens and closes a valve device by making contact to this diaphragm.

CONSTITUTION: A cover member 11 which is in the shape of a dish is fixed to the left-end flange portion 6b of a cylinder casing 6 by a fitting ring 11 through the external circumference bead portion 87a of a diaphragm 87. A spring retainer 84 in the shape of a dish makes contact to the diaphragm 87 and a spring 89 is arranged between the spring retainer 84 and a dividing wall body 85. A controll piece 97 is fixed in the center portion of the spring retained 84, and it is freely slidable in the center hole 103 of the dividing wall body 85 and it opens, closes and controls a valve device.