To obtain a new vitamin D intermediate useful as an intermediate for synthesizing vitamin D derivatives.

A compound of formula I (Tf is SO2CF3) is obtained by oxidizing vitamin D2 with ozone, reacting the obtained compound of formula II with, for example, t-butyldimethylsilyl chloride and a diol compound in the presence of a basic compound such as imidazole in a solvent such as THF at a temperature near to the ordinary temperature under stirring to protect the primary hydroxyl group, oxidizing the secondary hydroxyl group of the obtained compound of formula III having the protected primary hydroxyl group, reacting the obtained compound of formula IV with, for example, N- phenyltrifluoromethane sulfoimide and lithium diisopropylamide in THF solvent to obtain the triflate compound of formula V, and then releasing the protecting group from the primary hydroxyl group of the obtained compound of formula V.