SLIDE DOOR SUPPORT STRUCTURE

A slide door support structure (20, 20A, 20B) includes: a slide support mechanism (22, 22A, 22B) slidably supporting a door (13) that can open and close a door opening (11) of a vehicle body (12), and including a slide rail (60) in a mechanism arrangement portion (S4) on a vehicle body (12) side; a cover member (900, 900A, 900B) supported by the vehicle body (12) so as to be movable between a first position where the cover member (900, 900A, 900B) does not hinder the door (13) from moving with the aid of the slide support mechanism (22, 22A, 22B) and a second position where the cover member (900, 900A, 900B) at least partially closes the mechanism arrangement portion (S4); and a drive mechanism (92, 92B) for the cover member (900, 900A, 900B). The cover member (900, 900A, 900B) is located at the second position in the door (13) closed state. The drive mechanism (92, 92B) moves the cover member (900, 900A, 900B) from the second position to the first position in mechanical conjunction with movement of the door (13) to an open state.