Abstract: A method and a device for monitoring the quality of print formed in a printing process, in which a web running continuously in a printing machine is measured substantially continuously by at least one measuring means. In addition to the product to be printed, at least one image pattern, which is printed with at least one printing ink and surrounded by unprinted paper, has been printed on the web. Both the image pattern and the unprinted paper are measured by the same measuring means, or at least one runnability or condition monitoring parameter of the printing machine is measured. The obtained measurement results are compared, and at least one factor affecting the quality of the print on the basis of the comparison is determined.