Abstract: The invention concerns a procedure for controlling the quality of printing, wherein measuring marks (11, 12, 13 and 14) are placed on the printing base, such as a paper web, beside and/or among the actual printing are employed. A lighting unit (1) and an electronic camera (2) trained on the paper web (3) and the operation of the camera at least is synchronized with the transport speed in the printing process. With the camera (2) an image is recorded from a measuring area (9) on the paper web (3), which area contains measuring marks (11, 12, 13 and 14). The image is stored in an image memory (5). The image is taken from the image memory (5) to be processed, whereat the measuring marks are identified and located therein and on their basis the printing quality is checked.