To provide a driving system of high energy efficiency, capable of restraining a facility cost from getting high, by utilizing an existing facility at the maximum.

An air cylinder 10 is stored with a piston 102 in an inside of a cylinder 101. A pipe 31 is air-tightly connected to a cylinder chamber 101a, and the other end of the pipe 31 is air-tightly connected to the second cylinder chamber 201a of an air volume control part 20. The second piston 202 is stored in the air volume control part 20, and a volume of the second cylinder chamber 201a is changed by moving the second piston 202. A driving force from an electric motor 207 is transmitted to the second piston 202 via gears 206, 203, to be moved. The piston 102 of the air cylinder 10 is moved along arrow marks D₁, D₂, with a change of a volume in the cylinder chamber 101a in response to a volume change amount in the second cylinder chamber 201a of the air volume control part 20.