Abstract: A blood flow blocking catheter, comprises: a puncture needle component having a puncture needle capable of puncturing a vein; and a sheath that covers said puncture needle component, and a balloon catheter that can be inserted into and removed from a lumen of the puncture needle component and has at its distal end a balloon that can block off blood flow. With the present invention, a balloon catheter can be easily inserted into a vein, and the balloon inflated, without making a large incision in the vein. Therefore, the temporary obstruction of blood flow with a balloon catheter can be carried out more easily, and this simplifies the surgery and makes it less invasive. Thus, it is possible to obtain a blood flow blocking catheter with which vascular anastomosis can be performed more safely and in less time.