A compound represented by formula (II): (where Ar represents a phenyl group optionally substituted by 1 to 3 substituents selected from the group consisting of a halogen atom and a trifluoromethyl group, and R represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms) is produced by step A: reacting trimethyl oxosulfonium salt or trimethyl sulfonium salt with a base in a solvent, and removing the resulting solid to obtain a trimethyl oxosulfonium ylide solution or a trimethyl sulfonium ylide solution; and step B: reacting a compound represented by formula (I): and the solution obtained in step A, and the compound represented by formula (II) can be derived to a compound represented by formula (V): that is useful for production of an antifungal agent.