In an electric control apparatus (C) for a four-wheel steering system including an electric motor (56) the rotary angle of which is electrically controlled in accordance with a target steering angle of rear road wheels (RW1, RW2), and a hydro-mechanical tracer mechanism having a fluid control valve (36) the valve element of which is drivingly connected to the electric motor (56) to be displaced in proportion to the rotary angle of the electric motor (56), the tracer mechanism being arranged to steer the rear road wheels (RW1),(RW2)in proportion to a displacement amount of the valve element, the target steering angle is converted into a control value for rotation of the electric motor (56), and a drive signal indicative of the control value is applied to the electric motor (56). The electric control apparatus (C) is designed to greatly change the control value to and from zero when the target steering angle is less than a predetermined small angle approximately zero and to change the control valve in proportion to the target steering angle when the target steering angle is more than the predetermined small angle.