To etch a silicon oxide film at a high speed and high selectively without using hydrogen gas or carbon monoxide gas as an addition gas.

In this method, an object 1 to be processed is arranged in a plasma processing chamber 21, plasma 28 is generated in the plasma processing chamber 21, and a silicon oxide film formed on a face of the object 1 to be processed is etched. At the time of etching, a substance capable of producing CF+, CF2+ by the plasma 28, such as an organic low dielectric film 232 composed of an organic low dielectric material capable of producing CF+, CF2+ is arranged in the plasma processing chamber 21 to control etching characteristics of the silicon oxide film.