A fuel supply device has a cover member which is attached to an opening portion of a fuel tank and a pump unit comprising a pump. The cover member and pump unit are connected via a connecting portion where the pump unit is rotatably connected to the connecting portion. Further, the fuel supply device includes a fuel residual amount detection device which is attached to the pump unit and configured to detect the residual amount of fuel. The fuel residual amount detection device includes a gauge main body to which electric wirings are connected, an arm portion which is movably mounted relative to the gauge main body and a float which is attached to a leading end of the arm portion. The float is positioned above a lower terminal end of the base portion when the cover member is held and lifted while the pump unit rotates with respect to the connecting portion.