A method of controlling a scanning-type plasma processing apparatus using a phased array antenna, includes observing light emission of plasma generated inside a processing container through observation windows provided at multiple positions in the processing container, calculating an in-plane distribution of values representing characteristics of the plasma on a substrate, based on data on the observed light emission of the plasma, and correcting a scanning pattern and/or a plasma density distribution of the plasma based on the calculated in-plane distribution of the values representing the characteristics of the plasma on the substrate.