PROBLEM TO BE SOLVED: To carry out the control of-molds, bacteria, algae and mites by applying specific chemicals having the biological resistance to a fiber, heat-treating the resultant fiber, fixing a prescribed amount of the chemicals thereto and efficiently processing a textile product. SOLUTION: Four or more kinds of chemicals selected from the group consisting of nitrile-based compounds such as a haloisophthalonitrile derivative, pyridine-based compounds such as a pyridinethiol 1-oxide derivative, haloalkylthio-based compounds such as a haloalkylthiosulfamide derivative, organic iodine-based compounds such as an iodosulfonylbenzene derivative, a thiazole-based compound such as an isothiazolin-3-one derivative and benzimidazole-based compounds such as a benzimidazolecarbamic acid derivative having biological resistance are applied to a fiber in a dyeing step and/or a finishing processing step thereof together with a dye or a finishing agent and the chemicals in an amount of 0.01-5.0wt.% based on the fiber are then fixed to the fiber by heat treatment to process the textile product.
