PURPOSE: To print a Bold character by apparently supporting a Bold body to a face having no Bold body in a post-script printer.

CONSTITUTION: When the printing of Bold characters is required from an application program 5, a printer driver 3 sets a face name to be printed as Bold bodies by a face setting means 11, the direction needed for forming Bold characters is defined by a direction definition means 12, and a font code is output so that printing is conducted up to aimed character size while characters contracted by a font-code output means 13 are moved at every trace quality in each direction. When the printing of a page is needed, the printer driver 3 indicates the printing and discharge of the page to a printer 2 by a form discharge means 14. The printer 2 prints printing images corresponding to one page transmitted from a computer 1 while being interpreted by an interpreter 6, and discharges a form when printing is completed.