The aim of this final work was to calibrate the CNC milling machine using a laser interferometer. The introductory part of the final work describes what constitutes the testing of machine tools, under which conditions are this tests performed and with which measuring equipment. The ISO standard 230-2 is described. This standard deals with the determination of the accuracy and repeatability of the positioning of numerically controlled machine tools according to which the tests are performed. In the second part of the final work, a practical part was performed. It was performed in the laboratory of the Faculty of Engineering in Rijeka with the aim of measuring the accuracy of the positioning of the CNC milling machine axis by an laser interferometer. The deviation values of each axis of the CNC milling machine were obtained. Based on the obtained results, data analysis was performed and the possibility of reducing position deviations was suggested. Since the result of accuracy deviations is greater than that allowed by the machine tool manufacturer and the repeatability of the measurements does not deteriorate, position deviations must be reduced. A method of compensating the error step with which the positioning accuracy will be released within the permitted limits is proposed. This would make the necessary prerequisite for obtaining quality part on the machine tool.