A rust-preventive water-oil separating cleaner composition contacts a part to be cleaned to which an oil attaches. The composition separates the oil from the part, while providing the part with a rust-preventive property, thus forming an oil layer containing the oil. The composition contains an ethylene oxide additive (X) of monoalkyl amine represented by the general formula (1), and at least one compound (Y) selected from the group consisting of: an N-monoalkyl-N-(2-hydroxyalkyl)-iminoethylene carboxylate having a hydrocarbon group with a number of carbon atoms from 8 to 22; an acylated amino acid salt having a hydrocarbon group with a number of carbon atoms from 8 to 22; an alkyloyl sarcosinate having a hydrocarbon group with a number of carbon atoms from 8 to 22, and a tall oil fatty acid salt ##STR00001##