A hydraulic anti-skid apparatus which includes a cut-off valve disposed within a braking circuit connecting a master cylinder to a wheel brake cylinder, a bypass valve disposed within a bypass passage of the braking circuit, first and second pistons respectively arranged to control opening and closing operations of the cut-off valve and the bypass valve, the first and second pistons each being arranged to be applied at one end thereof with a hydraulic braking pressure from the master cylinder and at the other end thereof with a hydraulic power pressure from a fluid pump, a solenoid valve arranged to apply the power pressure to the first piston in its deactivated condition and to connect the first piston to a fluid reservoir in its activated condition, and a regulator valve arranged to control the power pressure applied to the first and second pistons in accordance with the braking pressure applied thereto. The regulator valve is arranged acts to cooperate with a check valve in response to the braking pressure thereby to produce a hydraulic pressure at a higher value than the braking pressure. An orifice element is further arranged to throttle the flow of pressurized fluid supplied to the first piston through the regulator and solenoid valves to maintain the power pressure acting on the second piston.