To provide wool which has not only good washing resistance but also other excellent physical properties.

This wool is produced by a method comprising charging wool, water, and a penetrating agent in an identical processing machine, subjecting the wool to an immersing pre-treatment at ordinary temperature, sequentially continuously charging an acidic solvent, a hypochlorite solution, and then a pyrophosphate solution at ordinary temperature or as a low temperature at suitable intervals, heating, and immersing for a constant time.