An electrophotographic image forming apparatus in which overheating or burning of a heater caused by fabricating units whose specified supply voltages are different from each other is prevented. Power from a main unit is supplied to the heater, which is in a photosensitive drum in a drum unit, for heating the photosensitive drum so as to be maintained at a specified temperature, through a connecter disposed between the main unit and the drum unit. The connecter is comprised of parts which are respectively disposed in different positions, depending on the specified supply voltages. The respective positions of the parts vary, in relation to a reference position, in a direction around the rotation axis of the photosensitive drum which is rotated when the drum unit is installed in the main unit. When the specified supply voltage of the main unit is equal to that of the heater, the parts are fitted to each other, thereby making electrical connection.