Thiophene, which is one of the major sulfur-containing compounds in crude oil as well as dibenzothiophene, was successfully desulfurized by the heterolytic cleavage of the C-S-C bond through the treatment with NaOH in supercritical water at 400degreesC. Thiophene was disintegrated into S2- and such carboxylic acids as formic, acetic, and succinic acids within I h.