Abstract: A compound A expressed by the following chemical formula (wherein R denotes an organic group including a hydrocarbon group, an alkanolamine group, an aromatic group and/or a group including a polyoxyalkylene adduct; m denotes a positive integer of 0 to 3 and can be represented by a plurality of values; and k denotes a positive integer of 2 to 6) and containing a chlorohydrin group at its terminal is brought into contact with cellulose fibers in an aqueous phase in the presence of an alkali metal compound so that the cellulose fibers are crosslinked at the molecular level. Thus, the crosslinking reaction occurs on the surface of the cellulose fiber, and the anti-fibrillation effect and deep dyeing effect can be obtained without damaging the soft feeling of the cellulose fiber.