An ink cartridge comprising: an outer package having a box-like shape; an ink container stored inside the outer package; and an engagement part inserted at one end of the outer package in which the ink container is stored, the ink cartridge being attachable to and detachable from a printer, wherein an ink supply section is provided in the ink container, the ink supply section comprising: a supply opening communicating an inside and an outside of the ink container with each other and being engaged with the engagement part; an inner plug having a plug part provided inside the ink container for opening and closing the supply opening and a shaft part extending from the plug part into the container; a biasing unit provided inside of the ink container for biasing the inner plug in a closing direction and characterized in that the ink cartridge comprises: a covering member extending in an axial direction of the shaft part and including a predetermined length of a guiding inner diameter portion that maintains the posture of the shaft part upon the sliding thereof regulating a sliding direction of the inner plug and other portions having an inner diameter larger than the guiding inner diameter, the covering member being configured to cover a part of the shaft part to prevent contact with the ink container when the ink container shrinks as a result of a decrease in a remaining amount of ink in the ink container. an outer package having a box-like shape; an ink container stored inside the outer package; and an engagement part inserted at one end of the outer package in which the ink container is stored, the ink cartridge being attachable to and detachable from a printer, wherein an ink supply section is provided in the ink container, the ink supply section comprising: a supply opening communicating an inside and an outside of the ink container with each other and being engaged with the engagement part; an inner plug having a plug part provided inside the ink container for opening and closing the supply opening and a shaft part extending from the plug part into the container; a biasing unit provided inside of the ink container for biasing the inner plug in a closing direction and characterized in that the ink cartridge comprises: a covering member extending in an axial direction of the shaft part and including a predetermined length of a guiding inner diameter portion that maintains the posture of the shaft part upon the sliding thereof regulating a sliding direction of the inner plug and other portions having an inner diameter larger than the guiding inner diameter, the covering member being configured to cover a part of the shaft part to prevent contact with the ink container when the ink container shrinks as a result of a decrease in a remaining amount of ink in the ink container. a supply opening communicating an inside and an outside of the ink container with each other and being engaged with the engagement part; an inner plug having a plug part provided inside the ink container for opening and closing the supply opening and a shaft part extending from the plug part into the container; a biasing unit provided inside of the ink container for biasing the inner plug in a closing direction and characterized in that the ink cartridge comprises: a covering member extending in an axial direction of the shaft part and including a predetermined length of a guiding inner diameter portion that maintains the posture of the shaft part upon the sliding thereof regulating a sliding direction of the inner plug and other portions having an inner diameter larger than the guiding inner diameter, the covering member being configured to cover a part of the shaft part to prevent contact with the ink container when the ink container shrinks as a result of a decrease in a remaining amount of ink in the ink container.