The present invention provides a PFO closing device for bringing septum primum and septum secundum into contact and joint with each other. The device includes clamping means and energy supplying means. The clamping means includes a needle part for puncturing the septum primum, and a clamping member for cooperating with the needle part in clamping therebetween the tissues having the septum primum and the septum secundum. The energy supplying means supplies energy for joining the tissues clamped by the needle part and the clamping member. The clamping means is mounted in a catheter so as to be protrudable from and retractable into the catheter.