A 4,5-dihydronaphtho[1,2-b]thiophene derivative expressed by the formula: ##STR00001## (wherein R.sup.1 is a C.sub.1 to C.sub.10 1-hydroxyalkyl group or a C.sub.1 to C.sub.10 acyl group, and R.sup.2 and R.sup.3 separately substitute in the 6-, 7-, 8-, or 9-positions, and are each independently a hydrogen atom, a halogen atom, a C.sub.1 to C.sub.10 alkyl group, a hydroxy group, a C.sub.1 to C.sub.10 alkoxy group, a C.sub.1 to C.sub.5 alkenyloxy group, a C.sub.1 to C.sub.5 alkynyloxy group, a benzyloxy group, or the like, provided that when R.sup.1 is an acyl group and R.sup.2 is a hydrogen atom, then R.sup.3 is neither a hydrogen atom nor an acetyl group), or a pharmaceutically acceptable salt thereof This is a novel compound that is effective in reducing triglyceride levels in the liver and reducing blood glucose levels.