To provide a fuel supply system in which fuel stored in a fuel storage tank formed in a housing main body can be supplied by a high-pressure pump provided in the housing main body in spite of a rapid acceleration or a rapid deceleration of an engine, two types of connectors, which is a first connector having a low-pressure pump having a connection port for a fuel supply pipe from a fuel tank and a second connector having no pump, can be selectively attached via a common connector mounting part formed on a wall surface of a housing main body, and by using a housing having therein the commonly used high-pressure pump, a fuel supply system using an external pump and a fuel supply system using no external pump can be respectively manufactured in accordance with the purpose of use.