To continuously and stably produce a tube to be bent having the high bending precision by arranging a displacement sensor to confirm an existing position of the tube to be bent on a reaction force receiving part side between a grip device and the reaction force receiving part.

A tube to be bent 3 is set at the objective position, the rear end is gripped with a grip device 4, and the tube to be bent 3 is clamped with a pressing device 2. A displacement sensor 6 is advanced to the measuring position against the tube to be bent 3 with a displacement sensor moving device 14, the original position before bending the tube to be bent 3 is measured, detected, this detected value is sent to a receiving part 11 and it is stored in a memory 12. Next, a reaction force receiving part 5 is advanced to a specified position and bending is executed by a theoretical bending amount calculated with a controller 7 while clamping the tube to be bent with a bending die 1 and a pressing die 2. Bending is executed efficiently by successively repeating while controlling bending with this controller 7.