Sulfonamide compounds represented by general formula (I), or salts thereof; and drug compositions containing the same (wherein each symbol is as defined in the description). These compounds serve as preventive or therapeutic agents efficacious against diseases which can be cured through decrease in blood sugar level and those which can be cured through inhibition of cGMP-PDE, relaxation of smooth muscle, bronchodilation, vasodilation, inhibition of smooth muscle fiber, or inhibition of allergy.