PURPOSE: To obtain a fiber material for machining paper excellent in surface qualities, paper strength and improved water holding property, and having low contraction fluctuation and a high density.

CONSTITUTION: Fibers comprised of <1 de polynosic fibers and having 4-6g/d tensile strength and <8% tensile elongation at the standard condition, 3-5g/d tensile strength and <10% tensile elongation at the wet condition, and generating fibrillation by an external force, are used for paper machining.