A pressing-bending machine with a device for detecting the lower and upper cross-members deflection, aimed at interacting with at least one crowning system, essentially made up of means suitable for detecting the elastic deformation on the lower and/or upper cross-member (1, 4) vertical axis recorded during the plate pressing-bending active phase, said means, supplying the machine management logic unit with a higher or lower value respect to an upper cross-member reference value, from this depending the intervention of at least the crowning system, and also in which, said means, being active on both cross-members, comprise a part engaged to the action cross-member and a part, interconnected with the first one, integral with a fixed external cross-member independent from the action cross-member, comprising a means (8) for detecting and communicating the deflection relative to this latter with respect to the fixed external cross-member.