To obtain the subject new tetrahydrobenzothiophene derivative useful for treating gastrointestinal diseases accompanying abnormal smooth muscle stresses, ulcers, obesity, diabetes, etc., as an agonist excellent in β3-adrenaline receptor selectivity, etc.

A new tetrahydrobenzothiophene derivative of formula I [X is H, a halogen; (n) is 0, 1; Y is H, a lower alkoxycarbonyl, carboxyl] or its salt. The compound of formula I is excellent in β3-adrenaline receptor selectivity and is useful for preventing and/or treating gastrointestinal diseases accompanying abnormal smooth muscle stresses, useful for improving stomach ache, nausea, emesis, epigastric area dysphoria, etc., accompanied by stomach ulcer, duodenal ulcer, gastritis, enteritis, cholecystitis, and further useful as an antiobestic medicine, antidiabetic medicine, etc. The compound of formula I is obtained by condensing a 2-amino-1-phenylethanol compound of formula II with a tetrahydrobenzothiophenecarboxylic acid of formula III and subsequently reducing the produced amide group.