A refueling pipe structure of a fuel tank includes a tank body, and an a refueling pipe which is connected to the tank body to extend upwardly therefrom. The refueling pipe is provided at its upper end with a refueling port into which a refueling nozzle can be inserted. The structure includes a flow direction limiting device mounted within the refueling pipe in the vicinity of the refueling port for guiding a fuel flow from a tip end of the refueling nozzle toward an inner surface of the refueling pipe, while limiting the fuel flow in a gyrate direction along the inner surface of the refueling pipe. Thus, the generation of evaporated fuel within the refueling pipe during refueling can be inhibited, and fuel can be smoothly introduced into the tank body.