PURPOSE: To provide a method for controlling a printing operation of a line printer in which a printing quality level of a print character particularly when one character is printed by dividing it by two print heads and a printing speed can be accelerated.

CONSTITUTION: A line printer has a plurality of printing heads fixedly arranged in a spacing direction and spaced as a single unit thereby to be shared by the heads to print one line, and comprises the steps of calculating whether print character with received data is disposed at a connecting seam between the heads or not (step S15), and altering, if the character is disposed at the seam between the heads (steps S16/19), shared areas of the heads in one line (steps S17, S18/S20, S21).