[Object] To provide an excellent pharmaceutical composition for preventing and/or treating vascular diseases.[Means for Solution] Useful to provide a pharmaceutical composition for preventing and/or treating vascular diseases, which comprises 1) a COX-1 selective inhibitor and 2) clopidogrel or a pharmaceutically acceptable salt thereof. The present invention is useful as an excellent pharmaceutical composition for preventing and/or treating vascular diseases is provided and is particularly useful as a pharmaceutical composition for preventing and/or treating arterial thrombosis, ischemic heart disease, ischemic brain disease, pulmonary embolism, peripheral circulation disorder, restenosis and reocclusion, essential thrombocytosis and so on is provided.