A Patent Foramen Ovale closing device for bringing septum primum and septum secundum into contact and joint with each other, said device comprising: clamping means including a needle part for puncturing said septum primum, and a clamping member for cooperating with said needle part in clamping therebetween the tissues having said septum primum and said septum secundum; and energy supplying means for supplying energy for joining said tissues clamped by said needle part and said clamping member; characterized in that said clamping means is mounted in a catheter so as to be protrudable from and retractable into said catheter, and said needle part consists of a plurality of mutually spaced and disposed wire members, said PFO closing device further comprising positioning and holding means (60,80,90,100) which includes a positioning part for positioning said needle part relative to said PFO, and a holding part for holding said septum primum so as to be non-retractable relative to the puncturing direction of said needle part. wherein said holding part of said positioning and holding means (60,90,90,100) has a curving mechanism for curving a distal end portion of a long operating member provided in said catheter so as to be movable forwards and rearwards, by protruding said, operating member from the distal end of said catheter and operating said operating member to move axially forwards or rearwards, and a distal end portion of said operating member holds said septum primum so as to be opposite to the direction in which said needle part punctures said septum primum, wherein said curving mechanism has a main tube passed through said catheter and capable of being operated externally, an operating member provided in said main tube so as to be movable axially forwards and rearwards is protruded from the distal end of said main tube, an intermediate sleeve body and a tip sleeve body are provided coaxially with said operating member, said tip sleeve body and said intermediate sleeve body are connected to each other by an elastic wire member, and a contact member brought into contact with said tip sleeve body by pulling said operating member is provided at a distal end portion of said operating member; and said tip sleeve body and said contact member brought into contact with each other by operating said operating member to move forwards or rearwards curve said elastic wire member and are displaced so as to hold said septum primum. clamping means including a needle part for puncturing said septum primum, and a clamping member for cooperating with said needle part in clamping therebetween the tissues having said septum primum and said septum secundum; and energy supplying means for supplying energy for joining said tissues clamped by said needle part and said clamping member; characterized in that said clamping means is mounted in a catheter so as to be protrudable from and retractable into said catheter, and said needle part consists of a plurality of mutually spaced and disposed wire members, said PFO closing device further comprising positioning and holding means (60,80,90,100) which includes a positioning part for positioning said needle part relative to said PFO, and a holding part for holding said septum primum so as to be non-retractable relative to the puncturing direction of said needle part. wherein said holding part of said positioning and holding means (60,90,90,100) has a curving mechanism for curving a distal end portion of a long operating member provided in said catheter so as to be movable forwards and rearwards, by protruding said, operating member from the distal end of said catheter and operating said operating member to move axially forwards or rearwards, and a distal end portion of said operating member holds said septum primum so as to be opposite to the direction in which said needle part punctures said septum primum, wherein said curving mechanism has a main tube passed through said catheter and capable of being operated externally, an operating member provided in said main tube so as to be movable axially forwards and rearwards is protruded from the distal end of said main tube, an intermediate sleeve body and a tip sleeve body are provided coaxially with said operating member, said tip sleeve body and said intermediate sleeve body are connected to each other by an elastic wire member, and a contact member brought into contact with said tip sleeve body by pulling said operating member is provided at a distal end portion of said operating member; and said tip sleeve body and said contact member brought into contact with each other by operating said operating member to move forwards or rearwards curve said elastic wire member and are displaced so as to hold said septum primum.