A carbonyl compound represented by following Formula (1): ##STR00001## wherein R.sup.1 represents hydrogen atom or an organic group; and R.sup.2 represents hydrogen atom or an organic group having a carbon atom at a bonding site with the carbonyl group in Formula (1), wherein R.sup.1 and R.sup.2 may be combined to form a ring with adjacent two carbon atoms, or an equivalent thereof is reacted with an unsaturated compound represented by following Formula (2): ##STR00002## wherein each of R.sup.3, R.sup.4, and R.sup.5 represents hydrogen atom, a halogen atom, hydroxyl group, or an organic group and wherein R.sup.3 and R.sup.4 may be combined to form a ring with adjacent two carbon atoms, or a precursor thereof, to yield a furan compound represented by following Formula (3): ##STR00003## wherein R.sup.3' represents R.sup.3, R.sup.5 or hydrogen atom; and R.sup.1, R.sup.2, R.sup.3, R.sup.4, are R.sup.5 are as defined above.