PURPOSE: To facilitate mechanical working and assembling of a free piston, by a method wherein a casing for a liquid pressure controlling valve is provided with a stepped part for restricting the movement of the free piston.

CONSTITUTION: A liquid pressure controlling valve mechanism 7 is constituted of a piston 8, proportioning spring 9 and valves 10, 11, and the valves in the two systems are contained in the casings 4, 5 on opposite sides of the free piston 20. When one of the systems is failed, the free piston 20 is moved so as not to move the valve in the other system, which movement is restricted by bringing an annular member 40 into contact with the stepped parts 30 provided for the casings 4, 5. Accordingly, since the movement quantity of the free piston is restricted, it is unnecessitated to provide the free piston itself with a groove or the like, and assembling of the valves is facilitated.