To stably mount a fuel tank on the side of a tractor body while increasing capacity as much as possible.

The fuel tank 26 is disposed on the side of the tractor body 2, the lateral width of the front part 26f of the fuel tank 26 is large and that of the back part 26g is small, the back part 26g is disposed between the tractor body 2 and a rear wheel and has the rear wheel side surface taken substantially along the shape of the front lower part of a rear wheel fender 20. A tank stay 29 is projected from the tractor body 2 toward the side, and the front half of the fuel tank 26 is fixed to the tank stay 29 via a stopping means 30.