Provided is a processing state detection unit includes: a light emission detection unit configured to detect light emission of the plasma; a calculation unit configured to obtain a differential waveform data of the light emission of the plasma; a database unit that stores a plurality of pieces of differential waveform pattern data in advance; a film thickness calculation unit configured to calculate an estimated value of the film thickness of the processing target film processed on the processing target material by weighting based on differences between the differential waveform data obtained by the calculation unit and the plurality of pieces of differential waveform pattern data stored in the database unit; and an end point determination unit configured to determine an end point of processing using the plasma based on the estimated value of the film thickness of the processing target film calculated by the film thickness calculation unit.