To enable detection of ultraviolet rdiation of all wavelengths with one ultraviolet radiation detector and judging the wavelength of a detected ultraviolet radiation lamp.

When ultraviolet radiation of 254 nm enters from an aperture 11, the radiation is subjected to fluorescence conversion by first phosphor 12 having sensitivity to all wavelengths, and received by only a first light receiving element 14. When ultraviolet radiation of 300-400 nm enters from the aperture 11, a part thereof is subjected to fluorescence conversion and received by the first light receiving element 14, and a part of the ultraviolet radiation which is not yet converted is subjected to phosphorescence conversion and received by a light receiving element 24. Residual unconverted ultraviolet radiation is absorbed by ultraviolet radiation absorber 25. Visible light is absorbed by visible light absorber 26.