PURPOSE: To enable automatic resetting of a plasma discharge by detecting the state that the plasma discharge by microwaves stops.

CONSTITUTION: This microwave plasma treating device 1 executes a treatment on a substrate by introducing microwaves and gaseous raw material into its discharge space and generating plasma. A discharge stop detecting means 4 is connected to the discharge space of the microwave plasma treating device 1. This discharge stop detecting means 4 detects the discharge stop state from the discharge potential and current, discharge power and discharge pressure of the discharge space. The treating device is provided with a discharge controller 6 for controlling the discharge according to the results of the detection. The discharge controller 6 transmits the respective detection signals detecting the discharge potential and current, discharge power and discharge pressure of the discharge space by a signal transmission cable 5 to a microwave oscillation source of a discharge generating source 3 and a gas supplying source. This discharge generating source 3 resets the plasma discharge of the microwave plasma treating device 1 by a discharge generating means 2 in accordance with the respective detecting signals.