To provide an insecticidal filament that includes an insecticidal active compound solid at a normal temperature (20C) kneaded therein and includes a high insecticidal effect.

The insecticidal filament is obtained by kneading a filament-forming thermoplastic resin with an insecticidal active compound solid at 20C and an organic solvent having a boiling point of 70C. The insecticidal filament having a core-sheath structure is obtained by kneading a thermoplastic resin forming a core part of filament with an organic solvent having a boiling point of 70C and kneading a thermoplastic resin forming a sheath part of filament with an insecticidal active compound solid at 25C.