PURPOSE: To facilitate excitation of growth material gas or doping gas, by a method wherein a microwave cavity resonator is installed, and only by making gas to be excited pass through a casing of a cell equipment, said gas is excited.

CONSTITUTION: A control equipment 10 is connected with a gas supply part to a discharge tube 8 and a microwave cavity resonator 9, and controls them. Said control equipment 10 is connected with an intensity sensor 10a for discharge light arranged in the vicinity of the discharge tube 8, and adjusts the generation amount of microwave from the microwave cavity resonator 10 and the pressure of discharge gas on the basis of discharge light intensity detection value. Hence the discharge light intensity is subjected to feedback control. Thereby growth material gas or dopant gas can be easily excited.