Device for controlling the sharpening state of a blade (2) having a cutting edge (20) delimited by two sides (21, 22) converging towards a plane (X) that contains the cutting edge itself. The device comprises two control surfaces each of which is in contact with a corresponding side (21, 22) of the cutting edge (20) and is connected with a transducer (R4), which produces an electrical displacement signal (S4) proportional to a displacement of the control surface with respect to said plane (X). Furthermore, the device comprises a processing unit (E) that receives said displacement signals (S4) and compares them, emitting an error signal if the comparison produces a value that exceeds a predetermined limit. The control surfaces are the surfaces that delimit an external groove (40) of a roller (4) that is free to translate along an axis (A4) perpendicular to said plane (X) and spaced from the blade (2) by an amount such that said cutting edge (20) passes in said groove (40).