The invention is directed to a hydraulic braking system having a master cylinder (10) in which a first piston and a second piston are slidably disposed to define a first pressure chamber (11) and a second pressure chamber (12). A valve device (24) is provided between the first pressure chamber and a reservoir (20). A first pressure control device (30, 31) is provided between the first pressure chamber and wheel cylinders (38, 39), and a second pressure control device (32, 33) is provided between the second pressure chamber and wheel cylinders (40, 41). A pump (27) is provided in a passage connecting the reservoir and the first pressure control device, and driven to supply a brake pressure from the former to the latter. When the valve device is actuated to block the communication between the first pressure chamber and the reservoir, and the pump is driven, the pressure in the first pressure chamber will be increased to move the second piston, so that the pressure in the second pressure chamber will be increased. Accordingly, the pressure in each wheel cylinder may be controlled by the first or second pressure control device without depressing the brake pedal.