Microwave control method

A microwave control method in a microwave plasma processing apparatus including a microwave generation unit configured to generate a microwave having a power corresponding to a set power, a waveguide configured to guide the microwave generated by the microwave generation unit to an antenna of a chamber main body, a tuner provided in the waveguide and configured to control a position of a movable short-circuiting plate such that an impedance of the microwave generation unit side is matched with an impedance of the antenna side, and a stub provided between the tuner and the antenna in the waveguide and insertable into an inner space of the waveguide, the method comprising:

• detecting the position of the movable short-circuiting plate which is controlled by the tuner for the microwave outputted by the microwave generation unit;
• determining whether or not a difference between a reference position and the detected position of the movable short-circuiting plate is within a tolerable range;
• and
• controlling an insertion length of the stub into the inner space of the waveguide when it is determined that the difference between the position of the movable short-circuiting plate and the reference position is not within the tolerable range.