Abstract: A slide door driving system of a motor vehicle comprises an electric power source and a door driving device to move the slide door between a full-open position and a full-close latched position with an aid of electric power from the electric power source. A manual switch is mounted in the motor vehicle. A control circuit is used for controlling the door driving device in accordance with operation of the manual switch. A so-called "permission switch" is connected to the control circuit. The permission switch is turned ON when an ignition switch for an engine of the vehicle is turned ON. The control circuit is provided with a judging circuit which makes an operation of the manual switch operative only when the operation of the manual switch is carried out under a condition wherein the permission switch is kept ON.