PURPOSE: To maintain a special character printing quality and to improve a printing speed by a method wherein an enlargement/reduction procedure is selected in accordance with the value of a character code to be enlarged/ reduced, and a conversion processing is conducted in accordance with a specified magnification.

CONSTITUTION: When a character of a code '1010' is enlarged by a factor of three, a microprocessor 1 reads the content of a latch circuit 11 and conducts a conversion processing in a magnification as specified in combination with a plurality of times of enlargement processings and reduction processings by giving priority to the magnitude of the character. Namely, factors for enlarging the character by a factor of three in the combination of an enlargement by 16/n times with a reduction by n/16 times are found by calculation. Next, the microprocessor 1 reads the font data of the code '1010' from a character pattern ROM 3, transmits it to an enlargement reduction circuit 6, and instructs the enlargement reduction circuit 6 to enlarge it by 16/3 times. When the largement processing is finished, the MPU 1 instructs the enlargement reduction circuit 6 to reduce the result by 9/16 times. In this manner, the character of the code '1010' is enlarged by a factor of three (16/3×9/16=3).