An ink cartridge mountable, in a mounting direction crossing with a direction of gravity, to a cartridge mounting portion provided with an ink receiving tube and a plurality of electrical connecting portions, said ink cartridge comprising: a casing including an ink accommodating chamber configured to accommodate ink to be supplied to said ink receiving tube, said casing having a first side surface in a position at a leading end with respect to the mounting direction, an upper surface and a bottom surface, the upper surface, the bottom surface, and the first side surface being defined on the basis of the orientation (attitude) of the ink cartridge at the time when the ink cartridge is mounted to the mounting portion; a tube inserting portion into which the ink receiving tube is insertable a substrate provided on said casing and having an area above said tube inserting portion, the area crossing with the mounting direction; a plurality of electrical contacts electrically connectable with the plurality of electrical connecting portions, said electrical contacts being arranged in the area in a direction crossing with a height direction which is from said bottom surface toward said upper surface; an engaging portion engageable with a locking lever provided in said cartridge mounting portion to maintain an inserted state in which the ink receiving tube is inserted in said tube inserting portion and a connected state in which said electrical contacts are connected with the electrical connecting portions, and a positioning portion provided in a position above said tube inserting portion and below said electrical contacts and engageable with a positioning member provided in the cartridge mounting portion to limit movement of said casing in a direction (X, Z) perpendicular to the mounting direction, wherein the engaging portion is provided in the position closer to said electrical contacts than to said tube inserting portion, and wherein said substrate is provided on said first side surface characterized in that the tube inserting portion is provided at said first side surface in a position closer to said bottom surface than to said upper surface. a casing including an ink accommodating chamber configured to accommodate ink to be supplied to said ink receiving tube, said casing having a first side surface in a position at a leading end with respect to the mounting direction, an upper surface and a bottom surface, the upper surface, the bottom surface, and the first side surface being defined on the basis of the orientation (attitude) of the ink cartridge at the time when the ink cartridge is mounted to the mounting portion; a tube inserting portion into which the ink receiving tube is insertable a substrate provided on said casing and having an area above said tube inserting portion, the area crossing with the mounting direction; a plurality of electrical contacts electrically connectable with the plurality of electrical connecting portions, said electrical contacts being arranged in the area in a direction crossing with a height direction which is from said bottom surface toward said upper surface; an engaging portion engageable with a locking lever provided in said cartridge mounting portion to maintain an inserted state in which the ink receiving tube is inserted in said tube inserting portion and a connected state in which said electrical contacts are connected with the electrical connecting portions, and a positioning portion provided in a position above said tube inserting portion and below said electrical contacts and engageable with a positioning member provided in the cartridge mounting portion to limit movement of said casing in a direction (X, Z) perpendicular to the mounting direction, wherein the engaging portion is provided in the position closer to said electrical contacts than to said tube inserting portion, and wherein said substrate is provided on said first side surface characterized in that the tube inserting portion is provided at said first side surface in a position closer to said bottom surface than to said upper surface.