Inverter type X-ray apparatus has been introduced and used several hospitals. Principle of inverter type X-ray generators are such as to convert the frequency of commercial power supply to high frequency and to control the high voltages for X-ray tube. Inverter generators are now on the way for futher development to elliminate single phase generators and three phase generators. We compared inverter type X-ray apparatus with conventional single phase 2 peak and three phase 12 peak, apparatus in the following aspects X-ray out put to tube voltage, linearity of X-ray out put to mA, HVL according to mA contrast to kV.