Provided is a fuel system that can reduce the amount of fuel in a second tank before the amount of fuel in a first tank. A fuel system includes: a first tank and a second tank that respectively store fuel; a fuel supply pump that supplies at least the fuel in the first tank out of the first and second tanks to a fuel consuming section; a transfer pump that transfers the fuel in the second tank into the first tank; and a fuel passage having an inlet in communication with an inner portion of the first tank, and an outlet in communication with an inner portion of the second tank. The fuel in the first tank overflows into the second tank through the fuel passage.