A 1-phenyl 1-thio-D-glucitol compound represented by formula (I) or the like: ##STR00001## or a pharmaceutically acceptable salt thereof or a hydrate thereof, or a pharmaceutical preparation comprising the same as an active ingredient is useful as a novel type of prophylactic or therapeutic agent for diabetes, diabetes-related diseases or diabetic complications, which inhibits both SGLT1 and SGLT2 activities to achieve not only suppression of glucose absorption from the digestive tract but also excretion of urinary sugars.