PURPOSE: To enable printing while connecting a section between adjacent underline characters even when the characters at a plurality of pitches are printed by making the breadth of a character pattern for an underline larger than that of fundamental pitches, scaling up and down the breadth of the character pattern to a plurality of the pitches together with the character pattern and conducting printing.

CONSTITUTION: A printer control section 1 reads an underline character pattern (b) from a character pattern section 4 by a data including a character code through an interface control circuit 2, and draws the character pattern (b) onto a RAM 3 as a bit pattern. When the drawing processing of one line section is completed, a printing mechanism section 7 is controlled through a printing-mechanism control circuit 6, and the bit pattern is printed successively. Accordingly, when the breadth of the pattern (b) is made larger than that of a fundamental pitch 10CPI in a character pattern ai for the pitch 10CPI and the breadth of the pattern (b) is drawn only by pitch width set to the RAM 3, a section exceeding pitch width set is not drawn, and a section between adjacent underline characters is connected and print ing is conducted even when the character pattern for 10CPI is processed electrically and characters at a plurality of pitches (9.5CPI and 17CPU) are printed.