PURPOSE: To obtain high-quality animal hair fibers excellent in both pill r,esistance and spinnability by imparting animal hair fibers such as wool with a specific organic reducing agent followed by adjusting the moisture content of the fibers to a low level and then heat treating for a short time.

CONSTITUTION: Animal hair fibers such as cashmere, alpaca or mohair are imparted with 0.8-1.8wt.% of a liquid organic reducing agent of the formula (R1 is a 1-10C alkyl or a hydroxyalkyl) (e.g. trishydroxypropylphosphine) followed by adjusting the moisture content of the fibers to 17-30 (pref. 17-23)wt.% and then heat treated at 100-120°C for a short time. The obtained high-quality animal hair fibers retain its wool touch feeling, cause no yellowing and are excellent in both pill resistance and spinnability.