Abstract: The present invention relates to a microwave plasma processing apparatus, suited for generating a plasma by using microwaves, and a processing method. Microwaves propagated through a circular waveguide are tuned in the space thereof by a microwave tuner that is installed to match the impedance, and are introduced in a uniform and most efficient state into a discharge block having a plasma-resistant inner surface that is enlarged in a tapered form through a microwave introduction window. Then, a processing gas controlled to a predetermined pressure by a gas supplying structure and gas evacuating structure is turned into a plasma which is more uniform and is more dense by interaction of a microwave electric field that is efficiently introduced and a magnetic field produced by a solenoid coil.