A toner cartridge includes a casing, a developing roller, a holder, a toner memory, an electrical contact and a wiring. The holder is positioned at an outer surface of one side in a first direction of the casing. The electric contact surface is positioned at an outer surface of one side in a second direction of the holder. The second direction crosses the electric contact surface. The electrical contact is positioned on an outer surface of another side in the second direction of the holder. The wiring electrically connects the electrical contact and the electric contact surface. The electric contact surface includes a first electric contact surface and a second electric contact surface. The first electric contact surface electrically is connected to the electrical contact through the wiring. The second electric contact surface electrically is connected to the toner memory.