An ink cartridge for supplying the ink in an ink reserving chamber via an ink supply port into a recording head has a differential pressure valve mechanism disposed between an ink flow port and the ink supply port in the ink reserving chamber, whereby the ink is supplied an adequate amount to the recording head by opening or closing the differential pressure valve mechanism in accordance with an ink pressure of the recording head. As a result, it is possible to supply the ink at a substantially constant pressure to the recording head without regard to the variation in the amount of ink or the movement of the carriage.