A fuel supply tank, comprising a tank body 7 which stores fuel, a fuel filter 13 disposed in the tank body 7, a fuel supply passage 27 for supplying fuel in the tank body 7 to a fuel injection apparatus 3, a fuel return passage 29 for returning excess fuel and vapor from the fuel injection apparatus 3 into the tank body 7. The fuel supply passage 27 and the fuel return passage 29 are connected to the clean fuel room 23 which is defined by the fuel filter 13, and separation of fuel and vapor is performed in the clean fuel room 23.