To automatically confirm a fitted die based on information of auxiliary dies from a working program.

A work W pushed and fixed with cooperation of a bottom die 13 and a top die 17 vertically movable and protruded to the rear part, is fold-bent to the upper direction or the lower direction with a bend beam 41. One or a plurality of auxiliary dies 81 are fitted to an auxiliary die holder 75 provided so as to be freely shifted to the right and left direction, in the bend beam 41 and shifted with an actuator toward the right and left direction of the bend beam 4 from a waiting position. To this auxiliary die 81, an auxiliary identifying instruments 95R, 95L are relatively shifted and the kind of the auxiliary die 81 is discriminated with the auxiliary die identifying instruments and it is detected whether the auxiliary die 81 exists or not. Further, when the auxiliary die identifying instruments are relatively shifted, the length and the fitted position of one or the plurality of auxiliary dies 81, are detected from data from whether the auxiliary die 81 exists or not, detected with the auxiliary die identifying instruments, and it is judged whether the auxiliary die 81 is nicely operated or not.