This paper deals with the Sautrāntika-Vasubandhu doctrine of momentariness(Kṣaṇikavāda) to reconsider its concept of the kṣaṇa(moment) with identifying views of the several Mādhyamikas. Hirakawa(1966) offers the fullest account of the doctrine of momentariness in the Abhidharmic tradition. The term, kṣaṇa is the smallest unit of time in the ancient India.In Hirakawa’s argument, the concept of the kṣaṇa and the momentary entities in the doctrine of the Sarvāstivādin is characterized by having duration after origination, and interval between cease and origination. On the other side, Hirakawa argues that the Sautrāntika and Vasubandhu pointed out that the kṣaṇa does not has duration, and there is not interval between cease and origination. In the words of Tani(2000), moreover, the Sautrāntika-Vasubandhu doctrine of momentariness overcome opposition of the Madhyamakakārikā. It should be viewed with reservation. The issue is, Does Vasubandhu really regard the kṣaṇa as durationless time? It was caused by equivocal attitude of Vasubandhu. Vasubandhu did not give clear answer as to why he didn’t set forth the measure of the kṣaṇa. In conclusion, the reason is because of contradiction between the buddhist doctrine of santati(stream) and spontaneous destruction(ākasmika-vinaśa) of momentary entities for the proof of the momentariness.