An actual plate thickness and actual material constants are measured during punching before bending. The measured information is reflected on the bending, so that the bending is performed efficiently and accurately. Punching is carried out for each blank developed based on a nominal plate thickness and nominal material constants in blanking before the bending of a work W. Then, an actual plate thickness distribution and an actual material constant distribution of the work W are calculated based on various data containing a ram stroke and a pressure detected in the punching.