An ink cartridge that is filled with ink and, used with the ink cartridge loaded into a printer includes a reservoir that reserves the ink, an outlet through which the ink is supplied to the printer with the ink cartridge loaded, at least one ink supply system that includes a channel that leads the ink from the reservoir to the outlet, and a sensor that detects whether the channel is filled with the ink or gas, an ink cartridge terminal that is electrically coupled to the sensor and makes contact with a printer terminal disposed on the printer upon loading of the ink cartridge. A detection region of the channel where detection is carried out by the sensor is previously filled with gas with the ink cartridge yet to be used. Whether or not the use of the ink cartridge is proper is determined based on information from the sensor.