This paper describes how to determine the quality of the cut of stainless steel made by plasma arc cutting. The introductory part describes the process of plasma arc cutting, its characteristics, types, the development through history, as well as the advantages and disadvantages of the similar thermal cutting processes. Related equipment for plasma arc cutting is also described, and so is the impact of cutting speed on the quality of plasma arc cutting. The introductory part also explaines the HRN EN ISO 9013 norm(standard) which determines the quality of the cut. The experimental part determined the quality of the cut on the sample of structural steel with the application of the listed norm. The experimental part was carried out in the Laboratory for Welding at the Faculty of mechanical engineering and naval architecture. Samples were cut with different speeds with having in mind the optimization of cutting speed due to the quality of the cut. After cutting, in the Laboratory for Precise Measurements of Length (LFSB) were measured certain quality features of the cut and the classification of individual class quality of the cut. On the device for surface roughness measurement, were measured different magnitudes of surface roughness, while the straightness and angularity tolerance were measured with the help of a universal measuring microscope. Surface roughness magnitudes Rz, the average height of prominences, and values of straightness and angularity tolerances were classified according to the HR EN ISO 9031 norm.