A jig (124; 224) used for filling an ink cartridge (1; 100) which has (i) an ink supplying portion (21, 30) provided to face an inner space of the ink cartridge so as to allow supply of an ink from the inner space therethrough, (ii) an air introducing portion (25, 26, 50) provided to face the inner space so as to allow introduction of an air into the inner space therethrough, (iii) a first valve member (32; 52) which is disposed in the ink supplying portion and which is biased in a biased direction that causes the first valve member to be placed in a closed position thereof inhibiting the supply of the ink from the inner space through the ink supplying portion, and (iv) a second valve member (32; 65) which is disposed in the air introducing portion and which is biased in a biased direction that causes the second valve member to be placed in a closed position thereof inhibiting the introduction of the air into the inner space through the air introducing portion, wherein each of the first and second valve members is moved, upon installation of the ink cartridge on a recording apparatus, in an opposite direction opposite to the biased direction, said jig comprising: a first valve-lifter (123; 225) operable to move one of the first and second valve members (32, 32; 65, 52) in the opposite direction away from the closed position thereof; and a second valve-lifter (122; 223) operable to move the other of the first and second valve members in the opposite direction away from the closed position thereof, wherein said first valve-lifter includes a first communication-passage establisher (123; 225) operable, when said one of the first and second valve members is moved away from the closed position thereof by said first valve-lifter, to establish a first communication passage in one of the air introducing portion (21, 30) and the ink supplying portion (25, 26, 50) in which said one of the first and second valve members is disposed, such that said first communication passage allows supply of the ink to the inner space of the ink cartridge (1; 100) through said one of the air introducing portion and the ink supplying portion, and wherein said second valve-lifter includes a second communication-passage establisher (122; 223) operable, when said other of the first and second valve members is moved away from the closed position thereof by said second valve-lifter, to establish a second communication passage in the other of the air introducing portion (21, 30) and the ink supplying portion (25, 26, 50) in which said other of the first and second valve members is disposed, such that said second communication passage allows discharge of the air from the inner space of the ink cartridge through said other of the air introducing portion and the ink supplying portion, said jig being characterized by further comprising an attachment body (121; 221) which holds said first and second valve-lifters (123, 122; 225, 223), so as to connect said first and second valve-lifters and the ink cartridge (1; 100), wherein at least said first valve-lifter (123, 225) is detachably held by said attachment body. a first valve-lifter (123; 225) operable to move one of the first and second valve members (32, 32; 65, 52) in the opposite direction away from the closed position thereof; and a second valve-lifter (122; 223) operable to move the other of the first and second valve members in the opposite direction away from the closed position thereof, wherein said first valve-lifter includes a first communication-passage establisher (123; 225) operable, when said one of the first and second valve members is moved away from the closed position thereof by said first valve-lifter, to establish a first communication passage in one of the air introducing portion (21, 30) and the ink supplying portion (25, 26, 50) in which said one of the first and second valve members is disposed, such that said first communication passage allows supply of the ink to the inner space of the ink cartridge (1; 100) through said one of the air introducing portion and the ink supplying portion, and wherein said second valve-lifter includes a second communication-passage establisher (122; 223) operable, when said other of the first and second valve members is moved away from the closed position thereof by said second valve-lifter, to establish a second communication passage in the other of the air introducing portion (21, 30) and the ink supplying portion (25, 26, 50) in which said other of the first and second valve members is disposed, such that said second communication passage allows discharge of the air from the inner space of the ink cartridge through said other of the air introducing portion and the ink supplying portion, said jig being characterized by further comprising an attachment body (121; 221) which holds said first and second valve-lifters (123, 122; 225, 223), so as to connect said first and second valve-lifters and the ink cartridge (1; 100), wherein at least said first valve-lifter (123, 225) is detachably held by said attachment body.