It is intended to provide a contrast medium for thrombus capable of binding specifically to a thrombus, lowering background noise and thus improving the resolution in a contrast examination for thrombus formation; and a method of detecting a thrombus by using the same. A contrast medium for thrombus comprising, as the active substance, a substance obtained by labeling a compound capable of binding to GPIIb/IIIa which is selected from among compounds represented by the general formulae (I) to (IV) and physiologically acceptable salts thereof, and a method of detecting a thrombus by using the same.