A medical stapler is a medical stapler used together with an endoscope and includes a flexible elongated member extending in a length direction of the endoscope, a wire inserted inside the elongated member and movable forward and backward with respect to the elongated member, a suture assembly connected to a distal end of the wire and being able to suture a gripped treatment target with a staple, an operation unit connected to a rear end of the wire and ejecting the staple from the suture assembly by moving the wire forward and backward, and an ejection restriction structure restricting ejection of the staple when a tension applied to the wire is equal to or less than a first tension caused by a change in shape of the elongated member.