To provide a fluid pressure cylinder device with equalizer function manually operable at slow speeds without forming an equalizer circuit on the outside and suitably operable by pressure in a pneumatic or hydraulic cylinder with a built-in piston.

In a fluid pressure cylinder device formed by fitting the piston 6 in the cylinder 5, a rather soft annular packing 11 is fitted into an annular groove formed in the outer peripheral surface of the piston 6, and relief passages 9a, 10, and 9a allowing the fluid to pass from one to the other side of the piston 6 or stop according to the pressure of the fluid received by the annular packing 11 according to the movement of the piston 6 or stop are formed at the proper positions of the annular groove 8.