A length of a melamine foamed block to be accommodated in an ink tank housing as measured in the longitudinal direction is dimensioned to be larger than a length of the ink tank housing as measured in the longitudinal direction. Thus, while the foamed block is accommodated in the ink tank housing, it is compressed in the direction orienting toward an ink feeding port from which ink is fed to a printing head, i.e., in the ink feeding direction. Consequently, the ink retaining force induced by the capillary force is not intensified in the compressing direction of the melamine foamed block, resulting in an ink feeding capability of the printing head being improved. On the contrary, the ink retaining force effective at a right angle relative to the compressing direction of the melamine foamed block is intensified.