In a developing cartridge, a developing roller including a developing roller shaft is configured to rotate around a first rotational axis extending in predetermined extending direction and to carry developer thereon. The cartridge also includes a developing electrode formed of a conductive material and to be electrically connected to the developing roller shaft. The developing electrode includes a main part and a protrusion protruding from the main part in the extending direction. The protrusion has a first portion, which corresponds to a circumferential surface of the protrusion. The cartridge further includes a gear having gear teeth on circumferential portion of the gear. The gear rotates about the protrusion and includes a covering portion covering the first portion and being rotatable with the gear.