An anti-skid apparatus for installation in a vehicle braking system having a regulator valve for producing a hydraulic power pressure in accordance with a hydraulic braking pressure from a master cylinder. A control cylinder is disposed in a hydraulic circuit connecting the master cylinder to a wheel brake cylinder, and comprises a cylinder body having a cylinder bore defined therein and a piston axially slidably disposed within the cylinder bore. This piston forms at its one end a pressure chamber communicating with the wheel brake cylinder, and is applied at its the other end with the hydraulic power pressure from the regulator. Disposed in the control cylinder is a normally open cut-off valve which normally permits the flow of the hydraulic braking pressure from the master cylinder into the pressure chamber and blocks the flow of the hydraulic braking pressure when the piston moves to an extent more than a predetermined distance from its initial position for decreasing the volume of the pressure chamber. And, a changeover valve is disposed between the regulator valve and the control cylinder, and applies the hydraulic power pressure to the piston or discharges it from the control cylinder.