An ultraviolet light permeable filter for an ultraviolet detection light is equipped on a filter glass surface with a dielectric multi-film layer which allows a visible radiation of wave length from 694 nm to 780 nm to reflect on the layer. The wave length also does not penetrate through the multi-flim layer. This filter prevents a reddish halation occurrence during an inspection display of a flaw detection light, which is the main cause of overlooking a scratch or flaw pattern.