To lower down a starting hydraulic pressure and obtain sufficiently large pedal reaction force, in a stroke accumulator of a brake hydraulic pressure control device.

A large diametric piston 32 is fitted, and a spring receiver 34 is inserted, into a stepped cylinder 30. A small diametric piston 36 is fitted into the large diametric piston 32. The spring receiver 34 is energized by a first spring 43 (large spring tension), and the small diametric piston 36 is energized by a second spring 45 (small spring tension). The first spring 43 is compressed by the large/small diametric pistons 32, 36 according to rising of a hydraulic pressure introduced to a pressure chamber 39 from an in/port 40, the second spring 45 is compressed by the small diametric piston 36 after the large diametric piston 32 is abutted to a stepped part 47, and the first spring 43 is again compressed by the small diametric piston 36 after an abutting part 48 is abutted to the spring receiver 34. A start hydraulic pressure is decreased by compressing the first spring 43 by thrust of the large/small diametric pistons 32, 36 (large pressure receiving area), and pedal reaction force is increased by compressing the first spring 43 by thrust of the small diametric piston (small pressure receiving area).