PURPOSE: To achieve high resolution and high quality and to enable high speed writing, by utilizing an electro-mechanical conversion element DMD as an optical writing element for a coloring paper adhered with photosensitive toner.

CONSTITUTION: When the maximum effective voltage being applied from a DMD drive circuit 25-9 onto a mirror array cell is ED and the swing angle of a micro mirror in a DMD element 25-8 at that time is θD, the reflection angle varies by 2θD at the maximum. If 2θD=∠AOD, and the voltage levels for satisfying a relation ∠AOB=∠BOC=∠COD are EB, EC, and a flush light source 5-5 is lighted temporarily only when the voltage is EB, EC or ED, the reflecting light passes through any one of light paths OB, OC, OD. The reflecting light passes through interference filters having different pass areas and transmittances, and taken out with the power obtained by averaging only specific frequency components then passed through lenses 5-11, 5-13, 5-15 and a slit in a slit board and projected onto a mead paper. Three types of capsule toner on the mead paper are hardened according to the wavelength of respective reflecting light and exhibit color through a fixing roller.