PURPOSE: To correctly print an illuminated content and make a copying of a certificate difficult by arranging sheet conveying means and a sensor, etc., for reading a specific print printed by a certificate content printer provided in a print head.

CONSTITUTION: When an issue of a certain certificate is designated from an input unit 7, a communication is conducted from a host computer through a communication unit 10, data necessary to issue the corresponding certificate is delivered, and then a sheet printed with a certificate content is discharged from a laser beam printer 2. The sheet is introduced between two guide plates 12-1 and 12-2. When the sensor 12-2 senses an end of the sheet, a drive guide roller 14 of sheet conveying means 4 is driven by a sheet conveying motor 15, and driven at the same speed as a sheet feeding speed of the printer 2. When the sensor 12-1 detects the end of the sheet, sheet feeding is controlled irrespective of the sheet feeding speed of the printer 2.