Abstract: 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.