Plasma processing method and apparatus

A plasma processing method for processing an object with a plasma generated in an apparatus including a plate-shaped electrode disposable opposite to the object to be processed under a pressure around atmospheric pressure, and a plate-shaped shaped insulator disposed adjacent to the plate-shaped electrode, the method including:

• supplying a discharge gas containing an inert gas to a vicinity of the object from a first linear gas exhaust port located between the plate-shaped electrode and the plate-shaped insulator, while supplying a discharge control gas to the vicinity of the object from a second linear gas exhaust port located on an opposite side of the plate-shaped insulator relative to the first linear gas exhaust port, wherein the discharge gas and the discharge control gas are different compositions;
• and
• supplying electric power to the plate-shaped electrode or the processing object, wherein the electric power is supplied simultaneously with the supplying of the discharge gas and the discharge control gas.