To provide a compact multistage expansion device which reduces a difference in external dimension between stages, increases design flexibility of a device cylindrical body, increases stiffness of the device, and improves assemblability and maintainability of components in the device.

The multistage expansion device comprises an outermost stage cylindrical body, an intermediate stage cylindrical body, and an innermost cylindrical body. The cylindrical bodies can be protruded successively from the inside of the outermost stage cylindrical body. In the multistage expansion device, a pulley around which a wire for pulling the intermediate cylindrical body is wound and which is movable integrally with the intermediate cylindrical body is disposed in the innermost stage cylindrical body.