The present invention provides a method for promoting plant growth, which comprises treating a plant with a compound represented by the following Formula (1): provided that a method for promoting plant growth which comprises treating plants with a compound corresponding to any one of the following (1) to (8) is 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, and (8) Ethyl 7-(trifluoromethyl)benzo[b]thiophene-2-carboxylate.