The present invention relates to a water-resistant organic thin film obtained by crosslinking, with organic nitrogen compounds, an organic thin film comprising an organic dye having an anionic group, wherein the organic nitrogen compounds are first, second, and third acyclic organic nitrogen compounds each having two or more nitrogen atoms per molecule, wherein the nitrogen atoms of each of the first, second, and third organic nitrogen compounds are each in a cationic group, and the relation A≤0.4 nm