To perform optimum brake hydraulic control and suppress the capacity of a reservoir to a minimum limit, by adjusting a distance between a valve seat and a valve element in accordance with a level of a current allowed to flow in a solenoid seating/unseating the valve element.

In a main body 41 of a solenoid valve 40A, a valve seat 41a is provided, in order to generate force A, a current a is allowed to flow in a solenoid As, a valve ball 44 is energized downward. In this way, an opening 43 communicating with a master cylinder in the main body 41 and an opening 42a, 42b communicating with a wheel cylinder are interrupted. Here, even in the case of large differential pressure Δ P of hydraulic pressure between a master cylinder side and a wheel cylinder side, a level of the current, that is, the force A is determined so as to hold an interruption condition. In the case of the valve ball 44 desired to be opened, the force A is changed in accordance with the differential pressure Δ P. That is, when a difference between a hydraulic pressure P1 in the master cylinder side and a hydraulic pressure P2 in the wheel cylinder side is Δ P1, a brake liquid level is adjusted by the current allowed to flow in the solenoid Sa.