To improve an oil and fat treating solvent aiming environmental protection.

This solvent is formed by adding 30-50% of a vegetable soybean lecithin rich in emulsifying stability as one of a solvent selected for cleaning a stuck heavy oil stains in the oil treating solvent formed by including a neutral nonionic surfactant having good biodegradability without containing phosphorus as a main ingredient (≥90%), adding 0.5-10% of plural reinforced microorganisms of a facultative anaerobe generating plural kinds of enzymes as metabolic products thereto and uniformly kneading at a temperature range which is a little over a normal temperature.