PURPOSE: To obtain the subject product having high antifouling effect against marine life, keeping the antifouling effect over a long period and resistant to the lowering of strength by using a mixture of two or more kinds of different thermoplastic resins and a phenoxy-containing arsenic compound as a raw material.

CONSTITUTION: The objective product is produced by mixing (A) a thermoplastic resin with (B) 5-50wt.% (based on 100wt.% of the component A) of a thermoplastic resin different from the component A and (C) 0.1-1wt.% (based on the sum of the components A and B) of an arsenic compound containing phenoxy group (e.g. 10,10'-oxybisphenoxyarsine), spinning the mixture, twisting a plurality of the obtained yarns to form net yarn and making a net with the yarn. The component A is preferably polyethylene resin or polypropylene resin and the component B is e.g. polystyrene resin.