The paper deals with an analysis of frequency characteristics scanned at the spindle of CNC machining centre Pinnacle PKVMC650S.It also points on the early diagnostics necessity of possible sources of unwanted vibrations to predict the behaviour of devices, to find out the life of devices and to improve the quality of machined surface. The method of the planned experiment was used as the research method. The aim of experiments was to measure the frequency characteristics and their effective values. The experimental measures were done at three cutting speeds during the machining, i. e. when the tool was in contact with the workpiece. Measures were processed by means of module NI 9234 software LabVIEW. The experimental measures have shown that the spindle of CNC machine does not show the critical vibrations, and it can be considered acceptable for unrestricted operations.