A fuel supply system includes: a flange mounted at an upper opening in a fuel tank; a fuel pump that discharges fuel in the fuel tank; a high-pressure filter that filters fuel discharged from the fuel pump; and a filter case that accommodates the high-pressure filter and includes an upper case and a lower case, the upper case integrally formed with the flange. The fuel pump is fitted to an underside of the lower case to be positioned substantially coaxial with the high-pressure filter.