The invention provides a method of detecting ozone expediently and with high sensitivity. The invention, therefore, is directed to an ozone indicator comprising (1) at least one color-change layer comprised of an ozone sensor ink and (2) at least one non-color change layer both formed on a substrate, said color-change and non-color-change layers being formed in such a manner that at least a part or the whole of at least one color-change layer can be exposed to an ozone-containing atmosphere when the ozone indicator is put to use. The invention is further directed to an ozone sensor ink containing an anthraquinone dye having at least one amino group selected from primary and secondary amino groups.