PURPOSE: To prevent the generation of waste toner when drawing data is developed on a frame buffer so as to exceed the width of printing paper.

CONSTITUTION: A form data control part 6 adds the printing mode controlled by a printing mode control part 5 and the data of a paper size to the form data received by an interface control part 1 to store them in a page buffer 8. A drawing part 3 develops the form data on the page buffer 8 on a frame buffer 9 as a printing image and outputs the printing mode and the data of the paper size stored in the page buffer 8. An excessive drawing data erasing part 7 compares two printing modes and the data of the paper size from the printing mode control part 5 and the drawing part 3 and, when the developed form data exceeds the width of printing paper, the form data corresponding to the part developed so as to exceed the width of printing paper is erased from the frame buffer 9.