Disclosed is a 1,3,2-dioxathiolan-S-oxide derivative as represented by the general formula (I): ##STR1## (where R.sub.1 and R.sub.2 are identical to or different from each other and each is a hydrogen atom or a lower alkyl group;X is a halogen atom, a cyano group, a lower alkyl group, a haloalkyl group or a phenyl group;m is 0 or an integer from 1 to 5; and when small m is greater than 1 each x can be the same or different andn is 1 or 2).A 1,3,2-dioxathiolan-2-oxide derivative of the compound as represented by the general formula (I-I) is prepared by reacting a hydroxymethylcyclopentanol derivative with thionyl chloride; and a 1,3,2-dioxathiolan-2,2-dioxide derivative (I-II) thereof is prepared by oxidizing the compound (I-I). The compounds (I) can be employed as fungicides and intermediate compounds for the preparation of azolylmethylcyclopentanol derivatives.