There is provided a method for producing a resin composition, the use of the resin composition for shaping filaments being effective to decrease the filament-cutting frequency in process of shaping the filaments, and a method for producing filaments using the resin composition produced by the method. The method for producing an insect-controlling agent-containing resin composition comprises melt-mixing 100 parts by weight of a polyethylene-based resin, 0.1 to 100 parts by weight of an insect-controlling agent-containing support and 0.01 to 10 parts by weight of an antioxidant at a temperature of 160 to 300 °C.
