A seat support structure for restricting the movement of a seat front end and facilitate the mounting of the seat, the seat support structure including a tank cover provided for a fuel tank supported by a body frame, a flange extending to the rear of a vehicle body and provided on the rear portion of the tank cover and a fastening groove which opens upward to fasten the flange thereto, the fastening groove being provided at the front portion of a seat located to the rear of the tank cover and of the fuel tank.