[Problem] A compound which can be used as a pharmaceutical, particularly a insulin secretion promoter or a agent for preventing/treating disease in which GPR40 is concerned such as diabetes or the like, is provided.[Means for resolution] It was found that an oxadiazolidinedione compound which is characterized by the possession of a benzyl or the like substituent binding to the cyclic group via a linker at the 2-position of the oxadiazolidinedione ring, or a pharmaceutically acceptable salt thereof, has excellent GPR40 agonist action. In addition, since the oxadiazolidinedione compound of the present invention showed excellent insulin secretion promoting action and blood glucose level-lowering action, it is useful as an insulin secretion promoter or an agent for preventing/treating diabetes.