A process cartridge is described. The process cartridge may include a developing unit and a toner unit detachably mountable to the developing unit. The developing unit includes a developer casing provided with an accommodating section for accommodating the toner unit. The toner unit includes a toner casing and an agitating member in the toner casing. The developer casing includes a first fixing member and a second fixing member opposite side of the first fixing member in relation to the accommodating section. The toner casing includes a first fixed portion received by and fixed to the first fixing member; and a second fixed portion disposed at the opposite side of the first fixed portion in relation to a rotation shaft of the agitating member and fixed to the second fixing member when the toner unit is attached to the developing unit.