The toner thickness on printing paper, which is printed by six laser printers with printing paper and photographic paper, was measured by laser scanning confocal microscope. The results show that the toner thickness data are fluctuated because of the rough surface of printing paper, whereas the date of photographic paper are more stable. Also the relationship of stroke width and toner thickness are obtained. This research provides a practicability for measuring toner thickness with laser scanning confocal microscope. As an effective factor, toner thickness can offer quantitive evidence for printing document examination and identity the printer combined with other examining method.