PROBLEM TO BE SOLVED: To provide a peptide having a short chain length and a high myostatin inhibitory activity. A peptide, a pharmaceutically acceptable salt thereof, or a prodrug thereof, which comprises the amino acid sequence represented by the following formula (1) and has 16 or less amino acid residues: [Selection diagram] None【課題】鎖長が短く、かつ高いマイオスタチン阻害活性を有するペプチドの提供。【解決手段】以下の式(1)で表されるアミノ酸配列を含み、アミノ酸残基数が16以下である、ペプチド、もしくはその薬学的に許容される塩、またはそれらのプロドラッグ。【選択図】なし