PURPOSE: To provide a correcting method for a deflection in a plate bending machine by which the influence of the deflection is completely eliminated, the occurrence of a defective article is reduced, and productivity can be improved in a plate bending work.

CONSTITUTION: Downward and upward hydraulic cylinders A1 to An and B1 to Bn consisting of at least three cylinders or more, are equipped opposite to one another at properly constant intervals between upper, lower die holders 3, 5 and upper, lower frames 1, 2. And, driving and controlling are respectively performed for each upper, lower hydraulic cylinders A1 to An, and B1 to Bn which are opposed to one another so that the upper and the lower die holders 3 and 5 are always aligned.