The invention relates to a trailer hitch structure that is capable of efficient absorption of an impact load of a rear end collision. A trailer hitch (1) connected to an end of rear frames (2) has, on each side, a fixed plate (3) fixed to a rear end surface of the corresponding rear side frame (2). The rear surfaces of the fixed plates (3) are connected to each other by a cross member (5). A hitch support (6) for supporting a hitch ball (6d) is provided at the center of the cross member. A front surface upper portion of each of the fixed plates (3) is supported by a hinge arm (12a) of a fixed bracket (12) fixedly installed to the corresponding rear frame (2), so as to swing freely in a longitudinal direction. During the rear end collision, if the impact load is applied to the trailer hitch (1), the trailer hitch (1) swings towards the front of a vehicle body in a state that the trailer hitch is supported by the fixed bracket (12). Therefore the trailer hitch can not be bent at the place ahead of the fixed bracket (12). The impact can be effectively absorbed in a short span.