Abstract: The invention refers to the field of bending presses for plate sheets and more precisely it refers to a process and a device for detecting the bending angle in real time when the press punch operates on the sheet placed above the matrix die. The process provides for the generation of at least two flows of compressed air in at least two matrix die points that are totally or partially covered by the plate sheet. The pressure variation during the bending step is measured and such variation is compared with sample pressure values. The device provides for a compressed air system with a pressure reducer that supplies four orifices and a servo-controlled device that performs a compensation.