A plasma processing apparatus or a plasma processing method having an improved yield, the plasma processing apparatus includes: a processing chamber arranged inside a vacuum container; a processing gas supply line connecting to the vacuum container, communicating with the processing chamber, and configured to supply processing gas having adhesiveness to the processing chamber; and a gas exhaust line for the processing gas connecting and communicating the processing gas supply line with a processing chamber exhaust line that is connected to an exhaust pump and communicates with the processing chamber, in which the plasma processing apparatus exhausts the processing gas in the processing gas supply line through the gas exhaust line and the processing chamber exhaust line in a state where supplying of the processing gas to the processing chamber is stopped between one processing step of etching the wafer and a subsequent processing step.