PURPOSE: To evenly print without becoming broken the light color characters close to the gray for the purposes of mourning, etc., with use of a black ink toner.

CONSTITUTION: The character data received from a host device 2 are evolved to a memory part 14 as the character font data on the dot image by a character font data evolving part 12 and a modified character processing part 13. The change of the dot density is instructed to a light color character processing part 16 with the operation of an operator applied to a dot density setting part 15 or by the control code given from the device 2. The part 16 generates the network pattern data to which the logical value is set for each dot in response to the designated dot sensity set value and calculates an AND to the character font data of the part 14. A print part 17 prints the characters on a form based on the calculation result of the part 16.