A medical stapler includes a first and a second grippers that are provided so as to be capable of opening/closing with respect to each other, and that can grip tissue therebetween. The first gripper includes a first contact surface being made to come into firm contact with one side of the tissue, and an ejection hole that is provided in the first contact surface and from which a staple is ejected. The second gripper includes a second contact surface being made to come into firm contact with the other side of the tissue, and an anvil portion provided in the second contact surface and having a curved surface that causes a needle portion of the staple to be bent. The first and second grippers are provided so as to allow relative positions thereof to be adjusted in a tangential direction of the curved surface.