an ink cartridge is detachably mounted on a cartridge holder . at least one first reflector is provided in cartridge holder . a reflective - type optical sensor includes a light emitter and a light receiver . the optical sensor is operable to form an optical path originated from the light emitter to the light receiver via the first reflector . a shading member is provided in the ink cartridge operable to shade the optical path when the ink cartridge is mounted on the cartridge holder . a second reflector is provided in the ink cartridge . the second reflector reflects light emitted from the light emitter and varies an intensity thereof in accordance with an ink amount remaining in the ink cartridge .