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): wherein R1 is a hydrogen atom or a halogen atom; R2 is a group represented by wherein each symbol is defined in the specification, or a salt thereof or a prodrug thereof.