A two-layered olefin-based resin pellet comprising a core layer formed of an olefin-based resin composition (A) and a sheath layer formed of an olefin-based resin composition (B) and laminated on the outer surface of the core layer, wherein said olefin-based composition (A) contains an insecticidal compound, a granular inorganic filler, a metal soap, and an olefin-based resin (a) having a relatively high solubility to the insecticidal compound; and said olefin-based resin composition (B) contains, as a main component, an olefin-based resin (b) having a relatively low solubility to the insecticidal compound.