An ink jet printer comprises at least one ink jet head, in which plural nozzles are arranged in an array in a main scan direction, and eject a droplet of ink to recording material respectively at an ejected amount according to information of an image. Feeder rollers feed the recording material relative to the ink jet head in a sub scan direction, to print the image to the recording material two-dimensionally. A thermal head includes plural heating elements arranged in an array in the main scan direction, for applying heat to the recording material respectively in a heating region. A system controller sets drying heat energy according to the ejected amount, and drives the thermal head to apply the drying heat energy to the heating region, to promote drying of the droplet in the heating region.