An ink-sack-replaceable ink cartridge, comprising: a cartridge body, the cartridge body comprising a bottom wall, two lateral walls extending upward in a vertical direction from two lateral sides of the bottom wall, and two end walls extending upward in the vertical direction from two ends of the bottom wall, the end walls and the lateral walls being connected so that the bottom wall, the lateral walls, and the end walls jointly surround and define a receiving space, the bottom wall comprising a through hole penetrating through top and bottom thereof, the through hole being formed through the bottom wall at a location adjacent to one of lateral walls, two positioning protrusions being formed on an inside surface of one of the lateral walls that is adjacent to the through hole and extending in a vertical direction, the two positioning protrusions being respectively located at two ends of the through hole, the two positioning protrusions each having a guide surface, the guide surfaces being smoothly connected to inside surfaces of the through hole; and a cartridge cover, the cartridge cover comprising a top wall and two side walls extending downward from two sides of the top wall, the cartridge cover being combinable with the cartridge body to close the receiving space; wherein a cartridge-body slide coupling section is formed on each of the lateral walls, and a cartridge-cover slide coupling section is formed on each of the side walls, each of the cartridge-cover slide coupling sections being slidably connectable with each of the cartridge-body slide coupling sections, so as to allow the cartridge cover to combine with and separate from the cartridge body through slidable connection for closing or opening the receiving space; wherein the ink-sack-replaceable ink cartridge further comprises an ink sack and a pressing board, the ink sack being received in the receiving space of the cartridge body, the pressing board being bonded to the ink sack, a sensing section extending downward from one side of the pressing board, the sensing section being positionable between the two positioning protrusions of the cartridge body and alignable with the through hole. a cartridge body, the cartridge body comprising a bottom wall, two lateral walls extending upward in a vertical direction from two lateral sides of the bottom wall, and two end walls extending upward in the vertical direction from two ends of the bottom wall, the end walls and the lateral walls being connected so that the bottom wall, the lateral walls, and the end walls jointly surround and define a receiving space, the bottom wall comprising a through hole penetrating through top and bottom thereof, the through hole being formed through the bottom wall at a location adjacent to one of lateral walls, two positioning protrusions being formed on an inside surface of one of the lateral walls that is adjacent to the through hole and extending in a vertical direction, the two positioning protrusions being respectively located at two ends of the through hole, the two positioning protrusions each having a guide surface, the guide surfaces being smoothly connected to inside surfaces of the through hole; and a cartridge cover, the cartridge cover comprising a top wall and two side walls extending downward from two sides of the top wall, the cartridge cover being combinable with the cartridge body to close the receiving space; wherein a cartridge-body slide coupling section is formed on each of the lateral walls, and a cartridge-cover slide coupling section is formed on each of the side walls, each of the cartridge-cover slide coupling sections being slidably connectable with each of the cartridge-body slide coupling sections, so as to allow the cartridge cover to combine with and separate from the cartridge body through slidable connection for closing or opening the receiving space; wherein the ink-sack-replaceable ink cartridge further comprises an ink sack and a pressing board, the ink sack being received in the receiving space of the cartridge body, the pressing board being bonded to the ink sack, a sensing section extending downward from one side of the pressing board, the sensing section being positionable between the two positioning protrusions of the cartridge body and alignable with the through hole.