Abstract: An anti-lock control apparatus of this invention has modulators each of which is disposed at a point between said master cylinder and each set of front and rear brakes. Each modulator has a stepped piston in its cylinder. In the cylinder, are formed a front output fluid chamber and a rear output fluid chamber both of which follow the master cylinder. The front output fluid chamber is connected to the front brake, while the rear output fluid chamber is connected to the rear brake. The front output fluid chamber normally communicates with the rear output fluid chamber and, during anti-lock operation, the communication between the front output fluid chamber and the rear output fluid chamber is cut off by a cut-off valve portion. Thus, the fluid pressure of the rear brake can be maintained at the fluid pressure in the cut-off state.