PURPOSE: To further miniaturize a low-pressure accumulator used for an antiskid brake control device.

CONSTITUTION: When a large quantity of a brake liquid is discharged to the low-pressure accumulator 11a of the first brake system A during the antiskid brake control, the brake liquid discharged to the low-pressure accumulator 11a is returned to a master cylinder by the pump 16a of the first brake system A. The brake liquid also flows into the first chamber 24a of a cylinder hole 24, and a floating piston 25 is slid to the second brake system B side. The brake liquid of the second brake system B flows into a low-pressure accumulator 11b. The brake liquid flowing into the low-pressure accumulator 11b is returned to the master cylinder by the pump 16b of the second brake system B.