In an antiskid control system, the acceleration of a vehicle wheel is detected and compared with a predetermined value. A first count value is incremented in response to the detection of the wheel acceleration exceeding the predetermined value. When this first count value exceeds a reference count within a first preset period, the road is interpreted as having a rough surface and a second count value is similarly incremented in response to the detection of the wheel acceleration exceeding the predetermined count. If the second count value does not reach the reference count within a second preset period longer than the first preset period, the road is interpreted as having a smooth surface. The gradient of brake hydraulic pressure of the vehicle is controlled in response to the different interpretation of the road surface.