A debeading device for tire changing machines includes a swing arm having a hinging end hinged to a base of a tire changing machine and swinging in a swing plane between an active debeading position toward the base and an inactive position away from the base; a debeading tool supported at a free end of the arm, opposite to the hinging end; an actuator for reciprocatingly rotating the arm between the active and inactive positions, which includes an externally screw-threaded member supported by the base and rotatably actuated by a motor and screwingly/unscrewingly engaged in a matingly threaded hollow member associated with the arm.