To perform air bleeding while avoiding lowering of the hydraulic control accuracy as much as possible by entering of the air in a suction line and a pump into a hydraulic control valve device or the like.

The air bleed method for a brake system for a vehicle comprises a reservoir 48, the suction line 49, the pump 50, a brake cylinders 20, 22, 24, 26, a supply line 58, and booster valves 60, 62, 64, 66 etc. The air in the suction line 49 and the pump 50 is exhausted to the outside by operating the pump 50 keeping the booster valves 60 etc be closed state, and by making brake fluid pumped from the reservoir 48 through the suction line 49 flow into the reservoir 48. The air bleed can be performed through a master cylinder 12 by installing an air bleed passage having an air bleed valve between a supply line 58 and a supply line 38.