A 4,5-dihydronaphtho[1,2-b]thiophene derivative expressed by the formula: (wherein R1 is a C1 to C10 1-hydroxyalkyl group or a C1 to C10 acyl group, and R2 and R3 separately substitute in the 6-, 7-, 8-, or 9-positions, and are each independently a hydrogen atom, a halogen atom, a C1 to C10 alkyl group, a hydroxy group, a C1 to C10 alkoxy group, a C1 to C5 alkenyloxy group, a C1 to C5 alkynyloxy group, a benzyloxy group, or the like, provided that when R1 is an acyl group and R2 is a hydrogen atom, then R3 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.