A four-wheel-steered vehicle is provided with a front wheel turning mechanism and a rear wheel turning mechanism which respectively turn front and rear wheels in response to the rotation of a steering wheel. The rear wheels are turned in the same direction as the front wheels when the steering wheel is turned while the vehicle is in a predetermined operating condition. A rear suspension system which supports a rear wheel has a wheel support which supports a rear wheel and is connected to a rear wheel turning rod of the rear wheel turning mechanism so that the rear wheel on the wheel support is turned about a king pin axis when the rear wheel turning rod member is displaced. Upper and lower arms are connected to the wheel support and guide the wheel support so that the rear wheel on the wheel support is turned about the king pin axis in response to displacement of the rear wheel turning rod. A coil spring is connected between the wheel support and the vehicle body and restrains vertical motion of the wheel support under the counterforce thereof, the coil spring being arranged so that the line of action of the counterforce is tilted with respect to the king pin axis so that it is not parallel to the king pin axis, does not intersect the king pin axis and is directed such that the counter force turns the wheel support in the toe-out direction of the rear wheel thereon.