An object of the present invention is to provide a DP receptor antagonist. A compound represented by general formula (I): (wherein all symbols are as shown in the specification) and a pharmaceutically acceptable salt thereof have DP receptor antagonistic activity and are also highly safe, and thus are useful as active ingredients of pharmaceuticals for DP receptor-mediated diseases. In addition, the compound represented by the general formula (I) and the pharmaceutically acceptable salt thereof also have good transferability to the central nervous system, and thus are particularly useful as a preventive and/or therapeutic agent for diseases associated with DP receptors present in the central nervous system among DP receptor-mediated diseases, that is, sleep-wake disorders.