An etching process state judgment method comprising: a spectral data obtaining step, in which an optical emission spectrum distribution is obtained by monitoring optical emission during an etching process of a plurality of wafers; a peak detection step, in which peaks are detected from the optical emission spectrum distribution at a specific time point during the etching process, to obtain peak characteristics; a common peak identifying step, in which peaks common to the wafers are identified among the peaks detected in the peak detection step; and a state detection step, in which the characteristics are compared regarding the common peaks, to detect a state of each wafer in the etching process.A state (anomaly or normalcy) of an etching process is detected from optical emission spectrum distribution at the time of etching process, by a simple method without assuming substances.