Clamping device (10) for an opening door (13) of an industrial machine equipped with a frame (12). The device (10) comprises first attachment elements (20, 21) for a first clamping of the door (13) to the frame (12), and second mechanical closing elements (30) including a selectively mobile attachment element (31) associated with the frame (12) and able to be inserted in a mating seating (23) provided on the door (13). The attachment element (31) is associated with an actuator group (35) which moves it on a plane (P) between an inactive position and an active clamping position wherein an operative extremity (32) thereof cooperates with the seating (23). The actuator group (35) comprises a cam (39) selectively made to rotate around an axis (x) thereof by means of activation of a drive member (38). The cam (39) moves the attachment element (31) on the plane (P).