An ink jet printer having a print head unit on which ink ejecting nozzles are arranged. The ink jet printer includes an ink supplying unit having a solid ink storage unit to store solid ink, and a heating unit to melt the solid ink into liquid ink, an ink reservoir to accommodate and store the liquid ink from the ink supplying unit, which is extended so as to correspond to the length of the print head unit, and a heater to heat the liquid ink, disposed in the lengthwise direction of the ink reservoir.