An object of the present invention is to provide a process according to which 5-ene-3-one or 3,6-dione derivatives of sterols can be synthesized with a better yield, as well as a process for production of lipid metabolism improvers, foods, drinks, and animal feeds containing the 5-ene-3-one or 3,6-dione derivatives of sterols.The process for production of 5-ene-3-one or 3,6-dione derivatives of sterols of the present invention involves preparing a culturing solution containing an Arthrobacter bacterium, which is a microorganism exhibiting a cholesterol oxidase activity, and then, adding to the culturing solution an equivalent amount of hexane so as to prepare a bilayer solution consisting of an aqueous layer and a hydrocarbon-based solvent layer. Thereafter, sterol, or a derivative thereof, is made as a substrate contained therein, a reaction performed with cholesterol oxidase at 30° C. for 2 days, and, ethanol then added to separate a hydrocarbon-based solvent layer. Thereafter, the layer is dried to a state of dryness by means of a vacuum dryer so as to obtain 5-ene-3-one or 3,6-dione derivatives.