An ink cartridge has an ink tank in which the ink is stored, and a shutter mechanism which is arranged in the ink tank. The shutter mechanism includes a lever which is supported swingably and which has one end provided with a shutter and the other end provided with a float. The mass and the volume of the float are set so that the first direction, in which the lever moves by the buoyancy and the gravity generated when the entire shutter mechanism is positioned in the ink, is opposite to the second direction in which the lever moves by the buoyancy and the gravity when a part of the float protrudes from the ink liquid surface. A residual amount of an ink is indicated without being excessively affected by any disturbance such as the surface tension of the ink.