A brake apparatus capable of applying a regulator pressure regulated by a regulator valve device to an assisting chamber, to obtain a smooth brake feeling, even when a brake pedal is operated by a vehicle driver, during an automatic braking operation. A first control valve is disposed in a power pressure passage for controlling hydraulic pressure in the assisting chamber to be increased. A changeover valve device is disposed in a regulator pressure passage for selecting either one of a communicating state and a shutting-off state of the passage. A second control valve is connected to the regulator pressure passage between the changeover valve device and the assisting chamber, and controls the hydraulic pressure in the assisting chamber to be decreased.