According to one embodiment, a printer includes an image forming unit, a coloring conversion unit, and a deterring unit. The image forming unit forms an image from a temperature-sensitive ink whose color is changed depending on a temperature on a medium. The coloring conversion unit converts a coloring state of the image of the temperature-sensitive ink by heating or cooling the image of the temperature-sensitive ink. The deterring unit provided between the coloring conversion unit and the image forming unit deters an air heated or cooled by the coloring conversion unit from flowing toward the image forming unit.