When a driver inserts a key into a cylindrical lock-type outside door switch and rotates it clockwise or counterclockwise, a slide door for an automotive vehicle is opened or closed automatically by motor power from the outside of the vehicle. Additionally, when the driver inserts the key into the outside door switch, and rotates it to an open position, the slide door is unlocked automatically before being opened; when the driver extracts the key from the outside door switch, the closed slide door is locked automatically. A motor is mounted on the slide door and a power supply is applied to the motor by means of a current collector. A pinion and rack are also mounted on the slide door to open or close the door. Such structure allows the slide door to be opened or closed manually or automatically.