PURPOSE: To obtain a cleaning agent for a printing plate surface having a great cleaning effect, by a method wherein an aqueous solution of a compound capable of reacting with zinc oxide to form a hydrophilic substance is mixed with a hydrocarbon solvent and a suspended liquid or emulstion comprising a surface active agent as a main constituent.

CONSTITUTION: The cleaning agent for the surface of an electrophotographic planographic printing plate is obtained by mixing (1) an aqueous solution of a compound capable of reacting with zinc oxide to form a hydrophilic substance, (2) a hydrocarbon solvent having an action of dissolving a planographic printing ink and (3) a suspended liquid or emulstion comprising a surface active agent as a main constituent and optionally containing (4) a water-soluble colloidal substance (5) a wetting agent and (6) one selected from molybdic acid, boric acid, nitric acid, phosphoric acid, polyphosphoric acid and water-soluble alkali metal salts thereof. The compound is component (1) is preferably potassium ferrocyanate or the like, and the solvent in component (2) is preferably a petroleum distillate having a boiling point of 120W320°C.