A control method which quickly adjusts a plasma processing apparatus to a desired pressure regardless of gas type, gas flow rate or target pressure simply by optimizing constants. The plasma processing apparatus includes: gas supply means which supplies processing gas to a low pressure processing chamber; plasma generating means which supplies electromagnetic energy to the processing gas in the low pressure processing chamber and generates plasma; exhaust means which exhausts gas in the low pressure processing chamber; gas pressure measuring means which measures gas pressure in the low pressure processing chamber; exhaust speed adjusting means which adjusts exhaust speed of gas to be exhausted by the exhaust means; and an arithmetic and control unit calculates an exhaust speed to make the gas pressure measured by the pressure measuring means equal to a target value, and controls the exhaust speed adjusting means according to the calculation result.