An ink cartridge in which gel ink that is to be supplied to an ink tank of an inkjet recording apparatus is reserved, includes an ink pack and an outer box. The ink pack includes an ink container formed of a soft film material in which the ink is contained and an ink lead-out section which guides the ink inside the ink container outside. The outer box houses the ink pack and has an ink lead-out opening through which the ink lead-out section is exposed outside. The outer box has a pressure applying opening formed therein through which the ink container is exposed and a pressure is capable to be applied to the ink container or has a first perforation line along which the outer box is to be broken to form the pressure applying opening is formed thereon.