Disclosed is a corrosion-free connector-structure of a fuel pump used in a vehicle fuel supply system. An electrical connector portion of a fuel pump is shaped into a square tube and its tubular wall is formed with a lock window for engagement with an engagement nail of a female connector and a fluid discharge port at an upper and lower portion thereof, respectively. As gasoline fuel level in the fuel tank lowers, the connector portion is exposed to air in the fuel tank and gasoline in the upper space within the connector portion or tubular wall pushes down and discharges water and degraded gasoline remaining in the lower space within the connector portion through the discharge port. Since water and degraded gasoline will not remain within the connector portion, electrical connector members or electrodes may be prevented from corrosion.