To produce hygroscopic polyester fibers excellent in hygroscopictiy and laundering resistance by forming fibers of a polyester compounded with a specific polyalkylene oxide and then graft-polymerizing a polyalkylene glycol derivation on the surfaces of the fibers.

The hygroscopic polyester fibers are produced by spinning poly(ethylene terephthalate) compounded with 0.1-15 wt.% polyalkylene oxide (e.g. polyethylene oxide) having ≥100,000 (pref. 500,000-4,000,000) weight average molecular weight to form fibers, forming cloth with the fibers and then graft- polymerizing a polyalkylene glycol derivative (e.g. a polyalkylene glycol diacrylate and/or a polyalkylene glycol dimethacrylate) having <100,000 (pref. 250-1,500) weight average molecular weight on the surfaces of the cloth.