To obtain a non-halogenated detergent excellent in detergency, having low flammability and having no adverse effect on environment by mixing at least one compound selected from dialkyl esters of three specified organic acids with N-methylpyrrolidone.

This detergent is obtained by mixing 50-90wt.% of at least one compound selected from dialkyl esters of an adipic, succinic or glutaric acid (wherein the alkyl groups comprise each a 1-4C alkyl, i.e., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, etc.) with 10-50wt.% N-methylpyrrolidone, and if necessary, other highly flammable solvent such as a glycol ether or γ-butyrolactone. If necessary, stabilizers such as antioxidants, for example, benzotriazoles, amines, alkanolamines and nitrous salts are added to this detergent.