An electronic key duplicating machine includes a base, on which a first support is mounted for a clamp for, at separate moments, an original key and a blank key, an optical reader sensing the bitting of the original key, and a milling cutter reproducing the bitting on the blank key, which are mounted on a second support rigid with the machine base, the clamp being movable along the X axis and the Y axis relative to the second support, a unit memorizing the bitting of the original key sensed by the optical reader and controlling and commanding movement of the clamp and operability of optical reader and milling cutter, wherein the second support is of C-shape with its opening facing the clamp, and the optical reader is mounted on horizontal branches of the second C-shaped support, while the milling cutter is mounted in the cavity defined by the horizontal branches.