A fuel supply device includes a pump unit that sucks stored fuel in a fuel tank from a suction port and discharges the fuel to an outside of the fuel tank. A pressure regulating valve performs pressure regulation of fuel discharged from the pump unit. The pressure regulating valve includes a return port having an opening facing in a separating direction away from the suction port, and returns surplus fuel generated by the pressure regulation from the return port into the fuel tank. A suction filter encloses an internal space where the suction port is open, and filters the stored fuel entering the internal space. The suction filter includes an expansion part to which the internal space is extended, and the expansion part is on a side of the return port that faces in the separating direction.