Providing a stent which can easily be indwelled in a blood vessel in a state such that a catheter can be projected toward an inside of aneurysm. The stent is a stent for use in medical treatment of an aneurysm (1) and includes a cylindrical stent body (10) provided on a peripheral wall and having a plurality of insertion portions (11) through each of which a catheter (7) is insertable and a plurality of valving elements (20) provided in the insertion portions (11) respectively. Each valving element (20) is opened when the catheter (7) is inserted through one of the insertion portions (11). Each valving element (20) is closed when the catheter (7) is pulled out of the insertion portion (11). This suppresses an outflow into a blood vessel of a coil (9) placed in the aneurysm (1).