To provide an organic fiber for reinforcing a resin, by which adhesiveness and dispersibility of the organic fiber with respect to the resin can be widely improved at a low cost and a resin molding excellent in mechanical properties such as strength and flexible rigidity, impact resistance, thermal dimensional stability and surface appearance can be obtained, and further to provide an organic fiber reinforced thermoplastic resin.

A treating agent including a modified polyolefin compound of 60-100°C melting point is applied onto an organic fiber surface by 1-20 wt.% expressed in terms of solid content to organic fiber weight to obtain an organic fiber for reinforcing a resin. An organic fiber reinforced thermoplastic resin is formed of a thermoplastic resin including the organic fiber for reinforcing the resin and content of the organic fiber for reinforcing the resin is 1-70 wt.% to weight of the organic fiber reinforced thermoplastic resin.