PURPOSE: A fluorescent agent not dyeing hydrous contact lens comprising aqueous suspension of ultrafine particles of polymer to which a fluorescent substance is added.

CONSTITUTION: The aimed fluorescent agent comprising aqueous suspension of ultrafine particles of polymer [preferable example; copolymer comprising a monomer such as (meth)acrylic acid (ester), (meth)acrylonitrile, styrene, vinyl acetate, etc.] having 0.5W2μ particle diameter, to which a fluorescent substance [preferable example; fluorescein, Rhodamine, riboflavin, fluorecuson, 5-dimethyamino-1-naphthalenesulfonic acid and their derivatives, etc.] is added. The addition method of the fluorescent substance is preferably carried out by covalent bond.