PURPOSE: To simplify the control of press brake robot by bringing the side adjacent to the side to be bent of the material in contact with the back gauge, and clamping the position separated by the prescribed distance from the back gage with the robot.

CONSTITUTION: A pressbrake-robot 2 turns the planar material 3, and carries the planar metal 3 in a press brake 1 so as to bring the short side in press contact with a back gauge 14. The pressbrake robot 2 clamps the position separated from the back gause 14 by the distance decided based on 1/2 of the length of an upper die 11 and 1/2 of the difference of the side to be bent and the die. In the case that the horizontal distance between the upper die 11 and the back gauge 14 is (b), the horizontal distance between the upper die 11 and the material clamping part 29 is (c), the width of the upper die 11 is 2a, and the length of the side to be bent is 2a+8, the planar material 3 is clamped by moving the material clamping part 29 so as to be b+c=a+4. Then the planar metal 3 is turned, the side to be bent is carried in the press brake 1 and is bent.