An anti-skid control apparatus comprises an anti-skid control means for controlling a pressure reducing valve and a pressure increasing valve, each of which operated for a target wheel when an anti-skid condition is established for the target wheel, the pressure increasing valve controlled in order to linearly change a pressure difference, an estimating means for estimating an occurrence of a factor by which the brake hydraulic pressure is fluctuated at the conduit connecting the master cylinder to the pressure increasing valve for the target wheel while the pressure increasing valve is controlled for the target wheel, and an output means for generating an output for maintaining the pressure difference during a predetermining time period in which the pressure increasing valve is controlled, when the occurrence of the factor is estimated.