A vascular anastomosis device includes a vascular fastener having a first ring and a second ring, and a vascular fastening mechanism. The first ring is provided a first groove and the second ring is provided with a first projection. In addition, the vascular fastener is disposed in the vascular fastening mechanism. The vascular fastening mechanism includes a first tube, a vascular supporting unit, an advancing ring, a third tube, and a spreading unit. The first tube is connected with a second tube. The vascular supporting unit is disposed in the second tube. Furthermore, the vascular supporting unit includes a vascular supporting body and a vascular spreader assembled on the vascular supporting body. The first ring, the second ring, and the advancing ring are assembled on the second tube. The third tube is disposed in the first tube. The spreading unit is disposed in the third tube.