The present invention is to provide the substituted piperidine compounds with appetite peptide II receptor agonist activity. Compound representated by formula (I), wherein each symbol as used in the description or its salt, has appetite peptide II receptor agonist activity, and is used as prevention or the therapeutic agent of hypnosia.本發明提供的是具有食欲肽II型受體激動活性的取代的哌啶化合物。式(I)所代表的化合物，其中，每個符號如說明書所述，或其鹽，具有食欲肽II型受體激動活性，並且用作嗜睡症的預防或治療劑。
