BRAKE CYLINDER DEVICE AND DISK BRAKE DEVICE

The present invention provides a small brake cylinder device that can increase braking force output from a brake output portion that moves along with a rod, while suppressing an increase in the device size. A piston 24 defines a pressure chamber 43 and surrounds the axis of the rod 22 inside a cylinder body 20a, and moves in a linear direction that is parallel to the movement direction of the rod 22. When pressure fluid is supplied to the pressure chamber 43, the piston 24 moves in the backward movement direction relative to the cylinder body 20a in resistance to biasing force from a rod biasing spring 23. Swinging members 46 of a force amplifying mechanism 25 swing due to being biased by the piston 24 moving in the backward movement direction, and moves the rod 22 by biasing it in the forward movement direction. Accordingly, the force amplifying mechanism 25 amplifies the drive force generated by the piston 24 and applies it to the rod 22. A brake output portion 21 moves in the forward movement direction along with the rod 22 and outputs braking force.