A slide door structure of an automobile which enables occupants to get in and out with ease even in a narrow parking space because the door of the automobile can be largely opened and capable of reducing the constraints on the design of the body of the automobile. Forward lower rail boards (11, 13) are positioned on the lower part of the body (1) at the front of a rear wheel house (5) when the slide doors (2, 3) are closed and, when the slide doors (2, 3) are opened, extracted from the front side of the rear wheel house (5) to the outside rear side of the body (1) by the rotation of a front link mechanism, and a rear lower rail board (12) is positioned on the lower part of the body (1) at the rear of the rear wheel house (5) when the slide doors (2, 3) are closed and, when the slide doors (2, 3) are opened, extracted from the rear side of the rear wheel house (5) to the outside front side of the body (1) by the rotation of a rear link mechanism.