This invention concerns a method for enzymatic preparation of 6-O-.alpha.-D-glucopyranosyl-D-sorbitol (1,6-GPS) from isomaltulose. It is specified that the isomaltulose is put into an aqueous reaction solution containing a unit having sorbitol dehydrogenase (SDH) activity, incubated, and then 1,6-GPS is recovered from the reaction solution.