PURPOSE: To provide an pneumatic circuit wherein a piston speed does not increase over a fixed speed even if a nocking phenomenon occurs in a pneumatic cylinder utilized as an actuator for moving an article at a constant speed in various devices.

CONSTITUTION: In this pneumatic circuit for controlling a cylinder, air is supplied into a cylinder 43 from one side piping ports 41 and 42, and also the air is discharged from the other side piping ports 42 and 41 to reciprocate a piston rod 46 and a piston 44 in a cylinder 43. A relief valve 71 and a check valve 72 are provided in parallel in an intermediate position of a line 52 connected to the one side piping port 42 of the cylinder 43 to form constitution so that wherein the pressure of air before discharge passing through the relief valve 71 can become to a set value or more.