An ink tank consists of a case body and a top lid. The case body consists of an inner case having an ink chamber and an outer case. The ink chamber is parted into an absorbent chamber containing ink absorbents, and a storage chamber storing ink. A space is provided as a heat insulating layer between the inner case and the outer case, for insulating the ink from heat energy radiated from a recording head. When manufacturing the ink tank, the absorbent chamber containing the ink absorbents is filled with the ink and the inner case is placed in the outer case. Thereafter, the top lid is attached to the case body in a vacuum, and the ink is injected in the storage chamber through ink injection holes formed through the top lid.