A method of detecting only protein dirt adhering to a contact lens speedily and easily in an inexpensive manner. In particular, a contact lens after wearing is sequentially immersed in a coloring reagent solution containing bromochlorophenol blue or tetrabromophenol blue and an acidic solution of 3 or below pH value to thereby effect coloring of only protein component adhering to the contact lens, and in the state of coloring, the protein dirt adhering to the contact lens is detected.
