The present invention provides an aqueous cleaning solution for aluminum-based metals which comprises an inorganic acid in an amount to provide a pH value of 2 or less, an oxidized form metal ion and a surfactant represented by the following formula (I)R--O--(EO).sub.n H (I)wherein R represents an alkyl group having on average 10 to 18 carbon atoms per molecule, n represents an integer of 8 or greater, and EO represents an ethyleneoxy group which may contain a small proportion of a propyleneoxy group. The degradation of cleaning properties due to the accumulation of lubricating oil or decomposition of surfactants is lessened even when the cleaning operation is carried out for a long period of time.