PURPOSE: To provide a brake fluid pressure control device which has high degree of design freedom of a split point and stable control characteristic and can do with a small required quantity of a brake fluid.

CONSTITUTION: A brake fluid pressure control device comprises a fluid pressure control piston 8 which makes its strokes with increase of brake fluid pressure, a speed reduction detecting means 17 whose angle of inclination is changed by the stroke of the fluid pressure control piston, and a cutoff valve 22 for disconnecting the communication between a supplied fluid pressure part from a master cylinder and a rear wheel brake fluid pressure part according to a signal from the speed reduction detecting means.