A prototype flexible bending machine was made on the basis of a new method, idea which proposes to penetrate the tube into the die. Since the area of bending is limited and the cross section of the tube is restrained by the die, flattening, buckling and wrinkling at the inner wall of the tube can be prevented. The tube can be bent to any radius by using ths system. The effects of penetrated load flattening factor, variation factor of thickness, and bending radius are examined under various bending conditions. The results are concluded as follows: (1) In the beginning of bending, the penetrated load reaches the, maximum, and thereafter, the load decreases and remains constant as the bending continues smoothly. As the bending radius decreases the load increases. (2) The flattening factor increases as the bending radius decreases. The flattening nearly be prevented by the choice of bending conditions. (3) The reduce thickness of the inner wall of the tube is nearly prevented.