To provide a plasma processing device capable of improving plasma processing capability without deteriorating the capability of surface activation process by ultraviolet irradiation of a UV irradiation means adjacently installed with a plasma supply means.

The plasma processing device includes: a UV irradiation means 1 for irradiating ultraviolet rays UV on the surface of an object S to be processed; and a plasma supply means 2 for supplying plasma P on the surface of the object S with the ultraviolet rays UV irradiated by the UV irradiation means 1, both means arranged adjacent to each other. An ozone ingress prevention means 3 for preventing ingress ozone generated at the plasma supply means 2 between the UV irradiation means 1 and the object S, is provided between the UV irradiation means 1 and the plasma supply means 2. By the ozone ingress prevention means 3, the UV irradiation means 1 and the plasma supply means 2 are spatially nearly blocked. Thus, the ozone generated at the plasma supply means 2 is prevented from ingress between the UV irradiation means 1 and the object S.