Fluid-pressure drive device for circuit breaker

The invention provides a fluid-pressure drive device for a circuit breaker, which can restrain pressure rise through simple structures, and has the characteristics of independent structure, low cost and high reliability. The drive device includes: a contact (2) including a moving contact (2b) and a stationary contact (2a); a rod (3) connected to the moving contact (2b); a piston (10) which is connected to the rod (3) and is slidably installed in a cylinder and which opens and closes the contact (2); a fluid pressure source (5) for pressure-feeding a working fluid; and a control valve for driving the piston (10). In the drive device, the piston (10) forms a partition between a supply pressure chamber (12i) communicated with the fluid pressure source (5) and a small pressure-receiving area chamber (9) which are on the moving contact side of the piston and a cylinder control chamber (17) on the opposite side of the piston, and the control valve controls supplying and discharging the working fluid to and from the cylinder control chamber (17).