According to a resectscope apparatus of the present invention, in order to control the output properly by discriminating electric characteristics of perfusion fluids, under control of the control circuit (101), a predetermined detection current is fed from the output transformer circuit (105) by using power, which does not produce an electrical breakdown even in the insulative liquid (161) or in the air. A predetermined lapse of time until the output is stabilized is waited. The sensor signal processing circuit (107) A/D converts and measures current values detected by the current sensors (106a) and (106b). Whether a treating electrode and a return electrode are in a conductive liquid, in an insulative liquid or in the air is determined. Then, the output control processing is performed.
