To easily and safely execute the changing work of a die and also to rapidly excecute the preparatory work and returning work before and after the die changing in a bending device in which the die changing is manually executed.

This device has a die changing switch 5 which is operable by operators, a front table 48 which is provided so as to be freely opened and closed and die-changing controlling means 4B for controlling the preparatory action and returning action before and after the die changing including the operation of the die changing switch 5, opening of the front table 48 and interruption of power sources D1, D2... as a control power source 1 is in a started state.