A bending order which provides a highest possible bending accuracy is determined. First a bending order generating section generates a plurality of bending orders possible for bending operation. Then, whether the bend angle of each bend can be measured in each generated bending order is checked by a measurement judging section. For each bend which has been determined as an objective bend "impossible to measure", a reference bend whose correction value for a die driving amount is to be used for calculating a correction value for the objective bend is set by a correction condition setting section. Weighting is carried out by a weight setting section based on the degree of the correlation between the processing factors of the objective bend and the processing factors of its associated reference bend, and the weights assigned to all the objective bends are summed by a weight sum computing section. Thereafter, a bending order selecting section evaluates the respective weight sums of the bending orders to select a suitable bending order and outputs the evaluation result to an NC device.