PURPOSE: To provide a surface treating or dry etching method and a plasma processing system in which contamination of a sample can be suppressed.

CONSTITUTION: The anode section comprises an anode electrode 14, an insulator plate 18 of SiO2 having conventional structure disposed immediately above the electrode 14, and a PTFE jig 16. In the plasma processing system, the entire surface of the anode electrode exposed to plasma, i.e., the surfaces of the insulator plate and the PTFE jig are covered with a polyimide coating 20 of same material as a sample 24. The polyimide sample 24 is placed on the anode section covered with the coating 20 and subjected to plasma processing.