The present invention relates to an organic electroluminescent device comprising a substrate, an organic electroluminescent element, and a photocatalyst layer, wherein the organic electroluminescent element includes: a first conductive layer provided on the substrate; an organic electroluminescent layer provided on the first conductive layer; and a second conductive layer provided on the organic electroluminescent layer, wherein the photocatalyst layer covers all or part of a light-emitting region of the organic electroluminescent element, and contains a photocatalyst and a co-catalyst, and wherein an absolute value of the difference (|R1−R2|) between the refractive index (R1) of the photocatalyst and the refractive index (R2) of the co-catalyst at a wavelength of 589 nm is 0 to 0.35.