In an optical printing apparatus for selectively exposing light with respect to a photosensitive recording medium to thereby form a gradation image thereon, there are provided; image data input device for entering more than 4 colors of spectral image data; storage device for storing thereinto the entered spectral image data in the unit of either 1 screen or 1 line; an optical head for outputting more than 4 sorts of light having different wavelengths from each other; and head driving device for converting the stored spectral image data into predetermined exposure time periods, and turning ON the more than 4 sorts of light so as to ON/OFF-drive the optical print head. As a result, this optical printing apparatus is capable of performing a high image quality recording operation. More specifically, a realistic image having a material feeling is formed.