PROBLEM TO BE SOLVED: To provide a method for pulverizing crystalline bio-fiber from which powdery bio-nanowhisker, capable of sufficiently suppressing cornification and formation of an aggregate and excellent in water re-dispersion property, can be easily and efficiently obtained.SOLUTION: A method for pulverizing crystalline bio-fiber comprises a step for pulverizing crystalline bio-fiber in a low dielectric constant organic solvent.SELECTED DRAWING: None