yarns 2 3 are spread the permeation of a resin or conrete into the yarns 2 3 is improved enabling a dense composite material having an improved strength to be obtained the sizing agent used for bonding between the monofilaments constituting the yarns of the carbon fiber may be known ones which have conventionally been used in this field examples of such an agent include epoxy resin acrylic resin and polyvinyl alcohol the method of disintegrating yarns in the yarn disintegrating step 12 may be any one capable of breaking the bonding between the monofilaments through a sizing agent and an appropriate method known in the field of synthetic fibers can be used specific examples of such methods include a method in which the sizing agent is dissolved e g dissolution of the epoxy resin by means of an organic solvent such as butyl acetate a method in which ultrasonic waves are applied thereto in water or hot water and a method in which physical impact force is applied thereto while applying ultrasonic waves these methods may be used alone or in any combination thereof the method of applying a physical impact force includes a method in which the textile weave is softly beaten and a method in which the textile weave is exposed to a bubble stream in water fig4 shows the relationship between the width of yarns constituting a textile weave after yarn disintegration and the thickness of the textile weave as.