To provide a plasma processing apparatus or an operating method of a plasma processing apparatus with improved yield. The plasma processing apparatus includes: a sample stage disposed in the processing chamber in a vacuum container; a plasma forming space in which plasma for processing a wafer is formed above the sample stage and a lower space communicated with the plasma forming space below; an exhaust port disposed at a bottom portion of the lower space; a heater for heating a lower portion of the vacuum container surrounding the lower space; a first vacuum gauge that detects a pressure in the processing chamber during the processing of the wafer; a second vacuum gauge for calibration communicated with an opening disposed in an inner wall of the processing chamber surrounding an outer periphery of the lower space below the first vacuum gauge; and a correction unit that is configured to correct an output of the first vacuum gauge by using outputs of the first and second vacuum gauges when a pressure in the processing chamber is at a pressure value regarded as 0 and at a plurality of pressure values higher than the pressure value.