An object of the present invention is mainly to provide a medical skin external preparation that is suitable for treating superficial skin infections, in particular, superficial skin infections accompanied by blister or erosion, etc. For example, the present invention can provide a medical skin external preparation containing 1-cyclopropyl-8-methyl-7-[5-methyl-6-(methylamino)-3-pyridyl]-4-oxo-1, 4-dihydro-3-quinolinecarboxylic acid and/or a pharmaceutically acceptable salt thereof as an active ingredient, and an alcohol and/or a fatty acid having 12 or more carbon atoms.