PURPOSE: To allow automation of shadow printing with satisfactorily matched character alignment in a document as a whole by developing pattern data corresponding to code data at a prearranged position of a bit map memory which corresponds to a dark printing color, and at the same time, developing the pattern data at a position shifted by a prearranged number of dots from a prearranged position of the bit map memory which corresponds to a pale printing color by means of a shadow printing command.

CONSTITUTION: Printing data is received from a data source 2, the received printing data is stored into a receiving buffer 4, and code data of one unit is read from the stored printing data. A shadow flag 7a is set by a shadow printing start command. When the shadow flag 7a is on, character pattern data of the corresponding character code data is allowed to develop at a normal development position of a black buffer 7b. Next, the normal development position is shifted slightly to the lower right by a prearranged number of dots. Then the character pattern data of character code data is allowed to develop at a development position which is slightly shifted to the lower right from the normal position of a red buffer 7c.