The present invention provides a
brake device for a vehicle capable of exhibiting a braking force corresponding to the amount of operation of a
brake operating member even when a power supply
system fails. The
vehicle braking device of the present invention includes: a
master cylinder (1), the master
piston of which is driven to move by the
servo pressure in the
servo chamber, and the main pressure of the master
chamber pressure changes through the movement of the master
piston; the mechanical
servo pressure generates device (44), the rest of the high-pressure source is connected to the servo chamber, and based on the
brake fluid pressure of the high-pressure source, the servo chamber generates a servo pressure corresponding to the
pilot pressure in the
pilot chamber; it is connected with the
pilot chamber to generate the required pilot pressure in the pilot chamber The electric pilot pressure generating device (41, 42, 43); the main pilot room
brake fluid path (511) connecting the main chamber and the pilot chamber, and the
vehicle braking device uses the pilot pressure when the power
system is normal. The generating device generates pilot pressure, and the main pressure is used as the pilot pressure when the power
system fails.