Abstract: An ink cartridge comprising sealing members sealing openings of both ends of the cartridge body, a holder cap fitted around the upper end of the cartridge body; a seal opener connected to the lower end of an operating shaft inserted through a guide hole in the upper end of the holder cap; an elastic member urging the seal opener in the upward direction to separate it from the upper sealing member; and a seal packing provided on the upper end surface of the seal opener and pressed onto the upper inner surface of the holder cap by the urging force of the elastic member to block an air inlet that is formed by a gap between the operating shaft and the guide hole, the operating shaft being pushed downward against the urging force of the elastic member to cause the upper sealing member to be torn open by the seal opener, thereby preventing the ink from flowing into the ink tank, as desired, which makes it possible to control the quantity of ink to be supplied to the ink tank.