The purpose of the present invention is to provide a glucokinase activator useful as a pharmaceutical agent such as an agent for the prophylaxis or treatment of diabetes, obesity and the like. The present invention provides a glucokinase activator containing a compound represented by the formula (I): ##STR00001## wherein R.sup.1 is a hydrogen atom or a halogen atom; R.sup.2 is a group represented by ##STR00002## wherein each symbol is defined in the specification,or a salt thereof or a prodrug thereof.