Abstract: Disclosed is a dry etching apparatus for etching an etched material located in an etching chamber by an etching gas plasma, which has: a plurality of emission detectors for detecting intensities of different wavelength components which are generated in etching reaction; an emission analyzer for analyzing an intensity ratio therebetween from the detected intensities; a process data computing circuit for computing a selectivity ratio and etching rate to different films from an output signal of the emission analyzer; and an etching parameter operational controller for feedback-controlling RF power, degree of vacuum and gas flow rate or gas flow rate ratio on the basis of an output signal of the process data computing circuit.