Abstract: A pressure generating apparatus for a hydraulic brake system, including a master cylinder having a pressure piston which partially defines a pressure chamber and which is advanced to generate a fluid pressure in the pressure chamber in response to an operation of a brake operating member. The apparatus further includes inhibiting device having a non-operated state for allowing the pressure piston to be advanced, and an operated state for inhibiting the pressure piston from being advanced, and a pressure changing device having a pressure changing chamber communicating with the pressure chamber. The pressure changing device operates to change a volume of the pressure changing chamber and thereby change the pressure chamber pressure. A controller is provided for controlling the inhibiting device and the pressure changing device, to change the pressure in the pressure chamber while the inhibiting device is placed in the operated state.