Abstract: A wheel speed control device in an antilock brake system prevents the wheels of a vehicle such as an automobile from locking while braking. First and second brake pressure controllers are provided in which the first is a conventional differentiation type brake pressure controller and in which the second is an integration type brake pressure controller. Thus, a state such as an excessively low slip speed resulting from insufficient brake pressure, which was difficult to detect with a differentiation type main brake pressure controller, can be detected. This makes it possible to precisely and effectively control wheel speeds by executing minor pressure increase in which the brake pressure is increased at a low rate.