PURPOSE: To obtain a snail killing agent controlling Gastropoda such as siebolds globular snail, slug or Achanadina fulica bringing damages to crops without causing environmental pollution and residual toxicity, containing crude saponin extracted from a plant of the family Theaceae as an active ingredient.

CONSTITUTION: A snail killing agent contains crude saponin extracted from one or more fruits of a plant of the family Theaceae or oil pressed refuse thereof as an active ingredient. Fruits of the family Theaceae Camellia such as camellia, sasanqua, and tea or oil pressed refuse of them are used as the extraction raw materials, the raw materials are individually extracted, the extracted solutions are mixed and crude saponin is extracted. Or premixed extraction raw materials may be subjected to extracting operation. Preferably the extraction raw materials are defatted by an organic solvent such as ethyl acetate or ether and the residue is used. The residue is ground and extracted with water or an alcohol, the extracted solution is concentrated to dryness, dissolved in a small amount of methanol, allowed to stand at 4W10°C for 24 hours and the precipitate is filtered off and collected.