PURPOSE: To provide yarn or woven or knit fabric comprising promix fiber with resistance to heat, water, friction, etc., without damaging gloss and touch of the fibers by subjecting the yarn or woven or knitted fabric to radical graft polymerization with a methacrylic acid hydroxyalkyl ester.

CONSTITUTION: Yarn or woven or knit fabric comprising promix fiber is immersed in an acidic processing bath containing a methacrylic acid hydroxyalkyl ester, especially ≤4C alkyl ester of monoethylene glycol, etc., at pH3-5, treated and subjected to radical graft polymerization treatment to provide promix fibers with excellent resistance to heat, water, friction and microorganism without damaging silky gloss and touch of promix fibers.