To provide a door capable of improving workability of work for connecting a slider to an arm, by preventing the movement of the slider of an arm stopper when carrying the door, without using a part such as a separate tape.

This door has a header cap 2a installed in an upper end part of a door end rail 1, and the slider 6 of the arm stopper slidingly installed in a locking groove 4 arranged in the longitudinal direction of a top rail 3. The header cap 2a has an insertion part 7 entering the door end rail 1 from above, a header blocking-up part 8 of the door end rail 1, and a slider engaging part 9 positioned in the locking groove 4 of the top rail 3. The slider 6 has a locking object part 10 freely engaging with and disengaging from the slider engaging part 9 of the header cap 2a, and an arm engaging part 35 rotatably and engageably-disengageably engaging with one end part of the arm 22 of the arm stopper. When one end part of the arm 22 is disconnected from the arm engaging part 35, the locking object part 10 of the slider can be locked on the slider engaging part 9 of the header cap.