Provided is a discoloration inhibitor with which it is possible to inhibit discoloration of plants due to physical/chemical stimulation. This agent for inhibiting discoloration of plants due to physical/chemical stimulation contains, as an active ingredient, at least one glucosamine selected from the group consisting of chitin, chitosan, chitin oligosaccharides, chitosan oligosaccharides, and glucosamine, as well as derivatives and salts of these.
