A novel endermic medicament having a consistency of a gel is proposed which is formulated, as a gel base, with non-ionic water-soluble cellulose ether, e.g., methyl cellulose and hydroxypropyl methyl cellulose, modified with a modification agent containing, in the molecule, an alkyl group having 6 to 26 carbon atoms and a functional group having reactivity with the hydroxyl group in the cellulose ether, e.g., stearyl glycidyl ether, decyl glycidyl ether and cetyl epoxide. The endermic medicament formulated with the modified cellulose ether is stable by virtue of the very little interaction between the active ingredients and the gel base and also can exhibit high percutaneous absorptivity of the active ingredients through the human skin.