A method of producing 6,6-dimethyl-3 -oxabicyclo [3.1.0]hexan-2-one comprising subjecting a cyclopropane compound of the formula (1): (wherein, R1 represents an alkyl group, R2 represents an alkyl group having carbon atom(s) of 1 to 10, a haloalkyl group having carbon atom(s) of 1 to 10, or an aryl group having carbon atoms of 6 to 10 optionally substituted by an alkyl group having carbon atom(s) of 1 to 10, and when R2 represents the alkyl group, R1 and R2 are optionally the same or different each other.) to any of the following reactions a), b) and c): a) an acid treatment reaction after an alkali hydrolysis reaction b) an acid hydrolysis reaction c) an enzyme hydrolysis reaction , then, removing an aqueous layer.