PURPOSE: To effectively prevent the leakage of electromagnetic waves from the window for monitoring by equipping a processor with a monitoring window for monitoring the emitted light of plasma by transmitting it to outside and an electromagnetic shield.

CONSTITUTION: A monitoring window hole 38 is positioned at the side of a process chamber 10, and it is formed in the shape of, for example, a circle in the vicinity of the height of plasma generated. And, a monitoring window 40 is provided in the position of this monitoring window 38. The monitoring window 40 is one for transmitting the emitted light of plasma generated in the process chamber 10, and it is equipped with a translucent member 24, a holder member 44, and an electromagnetic shield 50. In the electromagnetic shield 50, a transmission hole for plasma generation is secured since it is made in porous or mesh shape. Hereby, the electromagnetic waves generated in a processing chamber can be effectively prevented from leaking to outside.