PURPOSE: To safely carry out an exposure with excellent wavelength properties at low cost by irradiating a photosensitive recording medium with light whose energy ratio is flatly distributed in a visible ray region via an interference filter, as the light having a sharp spectral distribution with respect to three primary colors.

CONSTITUTION: The light from a halogen lamp 3 lighted by a printing start key becomes parallel light by a condenser lens 3a, and is made incident on an LCD shutter 4. The shutter 4 is controlled by a controller according to the image signals of three primary colors, respective filters 5R, 5B, and 5G are inserted into an optical path to obtain the light of red, green, and blue having sharp spectra, and a microcapsule sheet 20 is irradiated with the light via an optical lens 6, to sequentially carry out the exposure. When the exposure is finished, the sheet 20 is carried to pressurizing rollers 30a and 30b and overlapped on a development sheet 35 to be transferred. Further, the coloring of the sheet 35 is promoted by a thermal fixing device 50, and output as an image is carried out.