Though the research and the development in the field of machine tool was focused on high precision and high speed machine these days, traditional gear reduction device has been used to increase the cutting force which was transmitted from power source, motor In this study, analysis of 2 step gear reducer used in machining center spindle was carried out by using APM WinMachine which is commercial software for the analysis of machine element and system. For the analysis of this device, first of all, the analysis of power source and the transmitting of it were carried out. Then, machine elements like gear, shaft, bearing, and the forth, was analyzed in the view point of life time, static strength, stiffness, fatigue failure, etc. Consequently, we can estimate them and introduce new idea of the design modification of reduction device by this study.