Disclosed is a compact
brake cylinder device which, while avoiding increases in the size of the device, is capable of increasing the braking force outputted from a
brake output unit which moves together with a rod. A rod (22) is provided inside of a cylinder body (20) so as to freely move in the advancing and retracting directions of the cylinder shaft direction. A
piston (24) partitions a pressure chamber (44) inside of the cylinder body (20), surrounding the circumference of the rod (22), and moves in a linear direction parallel to the movement direction of the rod (22). By supplying a pressure fluid to the pressure chamber (44), the
piston (24) resists the biasing force of a biasing spring (23) and moves in the retracting direction relative to the cylinder body (20). At that time, a force-multiplication mechanism (25) converts the linear direction drive force generated by the
piston (24) to a rotational direction, moves the rod (22) in the advancing direction, and multiplies the drive force from the piston (24) to act on the rod (22). A
brake output unit (21) moves together with the rod (22) in the advancing direction and outputs a braking force.