To provide a valve having so good responsiveness as to be opened and closed only through a minute pressure difference formed between two spaces, and also to provide an ink cartridge equipped with the valve.

An ink chamber 100 and a valve accommodation chamber 54 are partitioned from each other by a deeper side wall 53, and the wall 53 has through-hole(s) 28. A valve element 31 of a check valve 30 has a tubular cylinder 33 to be put in tight contact with the wall 53. The cylinder 33 is provided with an inner wall 34, and the wall 34 extends in the direction crossing the center line 46 and has a cross section of a bent form. A spherical lid 35 is arranged in the center of the inner wall 34, and the inner wall 34 is provided with a through-hole 41 to permit the ink to flow. Because the inner wall 34 is flexible, the lid 35 makes displacement to block the through-hole 28.