PURPOSE: A plaster material capable of stably containing a drug without decomposing it, obtained by blending a plaster material consisting of a pressure- sensitive adhesive substance with root of Cocculus laurifolius A.P. DE CANDOLLE.

CONSTITUTION: A plaster material consisting of a pressure-sensitive adhesive substance such as acrylic pressure-sensitive adhesive, rubber pressure-sensitive adhesive, etc., is blended with 0.01W15%, preferably 0.02W2% calculated as fine powder finer than 100 meshes of root of Cocculus laurifolius A.P. DE CANDOLLE, a plant of the family Menispermaceae, used as a vermicide or diuretic in Chinese medicine or 0.002W10%, preferably 0.005W2% calculated as extract with a polar solvent. The plaster material is especially effective for phenolic hydroxyl group-containing compound (e.g. salicylic acid derivative or vitamin E) or amine compound (e.g. ethanolamine antihistamine) showing extreme reduction in content in the existing plaster materials.