PURPOSE: To provide a microwave plasma treatment device forming a high density plasma, capable of equalizing treatment such as etching and capable of increasing the speed of plasma treatment.

CONSTITUTION: Dielectrics 15 are mounted into a treatment chamber 10 in a microwave plasma treatment device. Or the dielectrics 15 are installed into the treatment chamber 10 so as to be able to divide the inside of the treatment chamber 10. Accordingly, the density of radicals in the vicinity of a sample 17 is equalized approximately and increased when treatment such as etching is conducted to the sample 17, thus allowing treatment such as etching uniformly at high speed.