A coach door of a vehicle is provided. The door includes a hinge assembly that has a first hinge hinged to a vehicle body and a second hinge hinged to the first hinge and engaged with a rear end of a rear door. An opening start device rotates the rear end of the rear door to the outside of the vehicle at an early stage of opening of the rear door and a closing end device rotates the rear end of the rear door to the inside of the vehicle at a last stage of closing of the rear door. A guide unit is configured to guide a front end of the rear door to move the front end of the rear door in a longitudinal direction of the vehicle at the initial stage of opening of the rear door and the last stage of closing of the rear door.