An ink supply device for use in an ink jet printer comprising a main ink chamber in communication through a communication hole with a sub-ink chamber containing an ink absorbing member therein. A meniscus film forming member covering the communication hole and communicating the main ink chamber with the sub-ink chamber; the member having a first surface facing the interior of the main ink chamber and an opposite second surface. An ink guide member extending into a lower portion of the main chamber and also being in contact with the first surface of the film forming member, wherein as ink in the main ink chamber is consumed a differential pressure between the first and second surfaces of the film forming member causes a gradual expansion of a liquid meniscus film into an air bubble on the film forming member to maintain a constant negative pressure in the main ink chamber.