A fuel supply system has a cover, a pump unit, and metal pipes. The cover and the pump unit are connected through the use of the metal pipes so as to be moved relatively each other. A case cover, covering the pump unit, has supporting portions, each of which has a through hole. Each metal pipe is inserted through the through hole and thereby guided to be moved in its axial direction inside the supporting portion. The supporting portion has a plurality of grooves. Therefore, sliding resistance between the metal pipe and the supporting portion is reduced, that is, the pump unit can be smoothly moved relatively to the cover.