Disclosed is a discharge processing apparatus for processing an object (1) to be processed by applying a voltage to a processing gap formed between an electrode (2) and the object (1) to be processed while using an aqueous process liquid as the process liquid. This discharge processing apparatus comprises an anti-corrosion power supply unit (26) for applying a predetermined voltage by using the object to be processed as a cathode and an anti-corrosion electrode (25) arranged opposite thereto via an insulating material (24) as an anode; a process liquid quality measuring instrument (22) for measuring the state of the process liquid; and process liquid quality controlling means (16, 17, 18, 19, 20, 21, 23) for controlling the pH of the process liquid to be within the range of 8.5-10.5 basedon the measuring results of the process liquid quality measuring instrument (22).