A slide door apparatus includes a body-side guide rail provided at a vehicle body, a door-side guide rail provided at a slide door, connection members each of which includes a guide roller rolling on a path formed by each of the guide rails, each of the connection members being connected to each of the guide rails, the slide door being configured to open and close a door opening portion formed at the vehicle body based on a movement of the slide door, one of the connection members being connected to the door-side guide rail and including a support arm which is rotatably connected to the vehicle body and at which the guide roller is provided, and a rotation restriction mechanism restricting the support arm from rotating at a position at which the support arm is positioned after rotating in association with an opening operation of the slide door.