The invention provides a pharmaceutical composition comprising at least one polypeptide of the following (a) to (d): (a) a polypeptide comprising the amino acid sequence of SEQ ID NO:1; (b) a polypeptide comprising an amino acid sequence comprising one or more amino acid deletions, insertions, substitutions or additions in the amino acid sequence of the above (a) and having a platelet aggregation inhibitory activity and/or a platelet adhesion inhibitory activity; (c) a polypeptide comprising the amino acid sequence of SEQ ID NO:3; and (d) a polypeptide comprising an amino acid sequence comprising one or more amino acid deletions, insertions, substitutions or additions in the amino acid sequence of the above (c) and having a platelet aggregation inhibitory activity and/or a platelet adhesion inhibitory activity, as an active component.