To obtain a detergent for a lithographic printing plate face which has excellent removing ability for dirt in various kinds of contamination and which sufficiently can maintain and show desensitization action for fat by incorporating aliphatic carboxylic acid esters into an oil phase.

An acidic detergent for a plate face is preferably made to 1 to 4 pH and an alkali detergent for a plate face is preferably made to 10 to 13 pH. The detergent contains aliphatic carboxylic acid esters in an oil phase. The aliphatic carboxylic acid esters are properly alkyl esters of satd. or unsatd. carboxylic acid having 12 to 18 carbon atoms. As for the aliphatic carboxylic acid esters, for example, methylesters, ethylesters, propylesters or butylesters of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid or linolenic acid can be used. The content of aliphatic carboxylic acid esters is properly 5 to 40 wt.% based on the total weight of the detergent for a plate face.