To increase radical density in the circumferential area, to improve the efficiency of plasma utilization and to execute treatment of a high process speed in a large area by emitting ultraviolet rays irradiating the inside of the plasma with light and executing the radicalization of neutral atoms to the side of a process treating chamber.

The side of wall face of a process treating chamber 8 of an airtight vessel 1 is provided with a light-emitting device 20 for emitting ultraviolet rays Q into plasma. Microwaves MW from a microwave oscillator 4 are introduced from the slit 3a of a microwave wave guide 3 into a plasma generating chamber 7. A gas for a process introduced into the plasma generating chamber 7 is activated in the plasma and passes through a punching plate 6. In the case that high frequency electric power is applied to the space between a punching plate 22 and the inside wall of the airtight vessel 1, a light-emitting medium in a translucent vessel 21 is excited and emits ultraviolet ray Q. The ultraviolet rays Q prevent the deactivation of the radicals of the gas passed through the punching plate 6 and radicalize neutral atoms.