A body organ expansion device (1, 20, 30, 40) comprising: a distal-side tube (2, 2a) having a guide wire lumen; a proximal-side tube whose distal portion is fixed to a proximal portion of said distal-side tube (2, 2a); a stent accommodation cylindrical member (5, 5a) which encloses a distal side of said distal-side tube (2, 2a) and is slidable toward a proximal end of said distal-side tube (2, 2a); a stent housed in said stent accommodation cylindrical member (5, 5a); and a pulling wire (6a, 6b) which extends inside said proximal-side tube, with one end portion thereof fixed to said stent accommodation cylindrical member (5, 5a) and is pulled toward said proximal side of said proximal-side tube to move said stent accommodation cylindrical member (5, 5a) toward a proximal side of said body organ expansion device (1, 20, 30, 40), wherein said distal-side tube (2, 2a) has a proximal-side opening which is open at said proximal side of said distal-side tube (2, 2a) and communicates with said guide wire lumen; and a stent-locking portion which is disposed at said distal side of said distal-side tube (2, 2a) and contacts a proximal end of said stent accommodated inside the stent accommodation cylindrical member (5, 5a), thus preventing said stent from moving to said proximal side of said body organ expansion device; and said stent is formed approximately cylindrically, housed in said stent accommodation cylindrical member (5, 5a), with said stent being compressed in an axial direction thereof, and expands outward and returns to a configuration before said stent is compressed, when said stent is implanted in an organism; said body organ expansion device (1, 20, 30, 40) further comprising an operation portion (9, 89, 90, 100, 200), disposed at a proximal portion of said proximal-side tube, which has a pulling wire winding mechanism for winding said pulling wire (6a, 6b) and moving said stent accommodation cylindrical member (5, 5a) toward a proximal side of said body organ expansion device. a distal-side tube (2, 2a) having a guide wire lumen; a proximal-side tube whose distal portion is fixed to a proximal portion of said distal-side tube (2, 2a); a stent accommodation cylindrical member (5, 5a) which encloses a distal side of said distal-side tube (2, 2a) and is slidable toward a proximal end of said distal-side tube (2, 2a); a stent housed in said stent accommodation cylindrical member (5, 5a); and a pulling wire (6a, 6b) which extends inside said proximal-side tube, with one end portion thereof fixed to said stent accommodation cylindrical member (5, 5a) and is pulled toward said proximal side of said proximal-side tube to move said stent accommodation cylindrical member (5, 5a) toward a proximal side of said body organ expansion device (1, 20, 30, 40), wherein said distal-side tube (2, 2a) has a proximal-side opening which is open at said proximal side of said distal-side tube (2, 2a) and communicates with said guide wire lumen; and a stent-locking portion which is disposed at said distal side of said distal-side tube (2, 2a) and contacts a proximal end of said stent accommodated inside the stent accommodation cylindrical member (5, 5a), thus preventing said stent from moving to said proximal side of said body organ expansion device; and said stent is formed approximately cylindrically, housed in said stent accommodation cylindrical member (5, 5a), with said stent being compressed in an axial direction thereof, and expands outward and returns to a configuration before said stent is compressed, when said stent is implanted in an organism; said body organ expansion device (1, 20, 30, 40) further comprising an operation portion (9, 89, 90, 100, 200), disposed at a proximal portion of said proximal-side tube, which has a pulling wire winding mechanism for winding said pulling wire (6a, 6b) and moving said stent accommodation cylindrical member (5, 5a) toward a proximal side of said body organ expansion device.