A four-wheel steering apparatus of a vehicle has a front-wheel steering mechanism for steering front wheels, a rear-wheel steering mechanism for steering rear wheels, a steering gear mechanism operatively connected to the front-wheel steering mechanism and effecting a steering operation, a steering angle extracting mechanism operatively connected to the steering mechanism and extracting the steering angle of the front wheels, the steering angle extracting mechanism comprising a restraining member movable axially along the axis of the front wheels in response to the steering operation, and a string member fixed to the restraining member and displaceable in the lengthwise direction thereof in response to the movement of the restraining member, and rear-wheel steering angle control mechanism operatively connected to the steering angle extracting mechanism for controlling the amount and the direction of steer to be transmitted to the rear wheels, the rear-wheel steering angle control mechanism comprising a rotatable member rotatable in response to the displacement of the string member, and a transmission member movably engaged with the rotatable member and movable in conformity with the amount and the direction of rotation of the rotatable member for transmitting the amount of movement thereof to the rear-wheel steering mechanism.