To provide a new method for attaching a hair-thickening hair material, which allows the technician to easily and quickly attach a hair-thickening hair material without needing advanced skills, and can effectively prevent the hair-thickening hair material from falling off even during shampooing and to provide a hair-thickening hair material fixture used for the method.

The method for attaching a hair-thickening hair material comprises an own-hair insertion step for inserting own hairs 3 into a hair-thickening hair material fixture 1 from one end thereof 1, the fixture being mainly composed of a rubber or a resin, formed in a tube form, and can shrink by heating, a hair material insertion step for inserting a hair-thickening hair material 2 into a hair-thickening hair material fixture 1 from the other end thereof 1 and a heating step, succeeding to the own-hair insertion step and the hair material insertion step, for heating the hair-thickening hair material fixture 1 to thereby allow it to shrink, wherein the hair-thickening hair material fixture 1 has a great number of raised fibers 14 bent at the tip sides formed on the inner circumferential surface thereof.