PURPOSE: To prevent a contact lens from changing color by incorporating a reducing agent or peroxide and at least one acid salt selected from polymerized phosphates, silicates and alginates.

CONSTITUTION: This agent contains a reducing agent or peroxide and at least one kind of acid salt selected from polymerized phosphates, silicates and alginates. As for the reducing agent, sodium thiosulfate, sodium sulfite, sodium hydrogen sulfite, or sodium pyrosulfite is preferably used. As for the peroxide, hydrogen peroxide, sodium percarbonate, sodium or perborate is preferably used. As for the polymerized phosphate, chain-state polymerized phosphate (sodium pyrophosphate, sodium tripolyphosphate or the like), cyclic polymerized phosphate (sodium trimetaphosphate, sodium hexametaphosphate, or the like) are used. As for the silicate, sodium metasilicate, sodium orthosilicate, or the like can be used.