A vehicle hydraulic brake apparatus includes a hydraulic pressure generator which generates a power pressure irrespective of operation of a brake pedal and a regulation valve which regulates the power pressure to a predetermined pressure corresponding to an operation force of the brake pedal and outputs it to an output chamber. A master cylinder generates a master cylinder pressure in a master cylinder chamber by forward movement of the master cylinder piston and a wheel brake cylinder is operated by the master cylinder pressure to apply braking force to a vehicle wheel. An auxiliary piston is located backward the master cylinder piston to define an auxiliary pressure chamber between the master cylinder piston and the auxiliary piston and to move the master cylinder piston forward by an auxiliary pressure in the auxiliary pressure chamber. A pressure modulating device decreases the predetermined pressure outputted from the output chamber to supply the auxiliary pressure to the auxiliary pressure chamber. A pressure chamber communicates with the output chamber of the regulation valve to bias the auxiliary piston backward by a pressure in the pressure chamber. The auxiliary piston is biased backward by both the auxiliary pressure in the auxiliary pressure chamber and the pressure in the pressure chamber when both of the hydraulic pressure generator and the regulation valve are a normal condition in which the predetermined pressure can be outputted to the output chamber of the regulation valve, and the auxiliary piston is moved forward by the operation force of the brake pedal to move the master cylinder piston forward when at least one of the hydraulic pressure generator and the regulation valve is an abnormal condition in which the predetermined pressure cannot be outputted to the output chamber of the regulation valve.