A body organ expansion device 1 includes a distal-side tube 2 having a guide wire lumen 21； a proximal-side tube 4 whose distal portion is fixed to a proximal portion of the distal-side tube 2； a stent accommodation cylindrical member 5 which encloses a distal side of the distal-side tube 2 and is slidable toward a proximal end of the distal-side tube； a stent 3 accommodated in the stent accommodation cylindrical member 5； and a pulling member 6 for moving the stent accommodation cylindrical member 5 toward a proximal side of the body organ expansion device. The distal-side tube 2 has a proximal-side opening 23 which is open at the proximal side of the distal-side tube； and a stent-locking portion 22 for preventing the stent from moving to the proximal side of the body organ expansion device. The outer diameter of the proximal-side tube 4 is set smaller than that of a portion, having a maximum diameter, which is disposed in a region of the body organ expansion device which is distal from the proximal-side tube.
