This method for promoting plant growth treats plans with the compound indicated in formula (1). However, methods for promoting plant growth and that treat plants with compounds corresponding to each of (1) to (8) below are excluded. (1) methyl 4-(trifluoromethyl)benzo[b]thiophene-2-carboxylate. (2) methyl 5-(trifluoromethyl)benzo[b]thiophene-2-carboxylate. (3) methyl 6-(trifluoromethyl)benzo[b]thiophene-2-carboxylate. (4) methyl 7-(trifluoromethyl)benzo[b]thiophene-2-carboxylate. (5) ethyl 4-(trifluoromethyl)benzo[b]thiophene-2-carboxylate. (6) ethyl 5-(trifluoromethyl)benzo[b]thiophene-2-carboxylate. (7) ethyl 6-(trifluoromethyl)benzo[b]thiophene-2-carboxylate. (8) ethyl 7-(trifluoromethyl)benzo[b]thiophene-2-carboxylate.
