Provided is a chemical volatilization body which maintains volatilization performance even if rained upon. A chemical volatilization body comprising a structural body provided with a mesh comprising a fibrous material including a normal-temperature-volatile pyrethroid insecticide component, is characterized in that: the fibrous material comprises resin filaments； and the water retention ratio, i.e. the amount of water capable of being retained by the structural body relative to the weight of the structural body, is in the range 0.005 to 0.5 inclusive.本發明提供一種即便於藥劑揮發體經雨淋之情形時，亦保持揮發性能之藥劑揮發體。本發明之藥劑揮發體係包含具有絲網之結構體者，上述絲網包含含有常溫揮發性擬除蟲菊酯系防蟲成分之纖維狀物，上述藥劑揮發體之特徵在於：纖維狀物包含樹脂長絲，相對於結構體之重量的上述結構體可保水之量即保水比為0.005以上且0.5以下。
