Abstract: The invention relates to a folding door with a door leaf (4) which is movable between a closed position and an open, folded position, in which the door leaf (4) is folded about folding lines between opposite side edges (5) of the door leaf. A plurality of guide members (110-118) are connected to the side edges (5) in a spaced-apart relationship along the same, and two side frames (1) are extended adjacent to a respective side edge (5). Each side frame (1) defines at least a first and a second guide groove (68, 69), which are juxtaposed transversely of the side frame. The guide members comprise, at each side frame (1), a first set of guide members running in the first guide groove (68) only, as well as a second set of guide members running in the second guide groove only (69).