FOLDING DOOR

PROBLEM TO BE SOLVED: To provide a folding door which can be easily constructed. SOLUTION: This folding door 1 is provided with a door 13 and a frame 11, the door 13 is provided with a first door 15 on the hanging side, a second door 17 on the door end side rotatably connected to the first door 15, a door roller 23 at an upper end of the second door 17, an upper engagement part 62 at an upper part on the hanging side of the first door 15, and a lower engagement part 61 at a lower part on the hanging side of the first door 15, and an upper frame 3 of the frame 11 is provided with a frame main body 3c having an upper wall 3a and an inner wall 3b, and an outer wall member 10 installed on the frame main body 3c at a position facing the inner wall 3b. The inner wall 3b of the upper frame 3 is provided with an inner rail 41 on which the door roller 23 runs, a lower corner part 50 on the hanging side of the frame 11 is provided with a counter lower engagement part 51 in which the lower engagement part 61 is rotatably engaged, an upper corner part on the hanging side of the frame 11 is provided with a counter upper engagement part 53 in which the upper engagement part 62 is rotatably engaged, and when the lower engagement part 61 is engaged with the counter lower engagement part 51 to dispose the door 13 in the frame 11, the door roller 23 can be placed on the inner rail 41, with the outer wall member 10 installed on the frame main body 3c.