PROBLEM TO BE SOLVED: To provide a new anticoagulant especially suitable for an application requiring quick inhibition/control of blood coagulation.SOLUTION: This anticoagulant contains any one of (1) Staphylococcus aureus superantigen-like protein 10 (SSL 10) or its partial peptide showing Gla domain binding property, (2) a polypeptide equivalent to (1), and (3) a modifier of (1) or (2).【課題】迅速な血液凝固の阻害・抑制が要求される用途に特に適した新規抗凝固薬を提供すること【解決手段】(1)黄色ブドウ球菌スーパー抗原様タンパク質10(SSL10)又はGlaドメイン結合性を示すその部分ペプチド、(2)(1)の等価ポリペプチド、或いは(3)(1)又は(2)の修飾体のいずれかを含む抗凝固薬が提供される。【選択図】なし