To provide a gate door which is easy in adjusting a mounting position of a door body and also is excellent in an appearance.

The gate door includes a cover member 1, a support arm 2, a pair of holding members 3a, 3b, a fixing member 4 and a drawing tool 5. The cover member 1 is mounted on a side face of a column body 6 and forms a space with the column body 6. The support arm 2 extends laterally while having a door-suspending part 21 at one end and inserting the other end into the cover member 1. The holding members 3a, 3b holds the support arm 2 at any desired position in the horizontal direction in the cover member 1 and are free to pivot around a vertical shaft together with the support arm 2. The fixing member 4 is provided inside the cover member 1 and is free to contact with or separate from the holding members 3a, 3b. The drawing tool 5 is engaged with both of the cover member 1 and the fixing member 4 so as to draw the fixing member 4 contacting the holding members 3a, 3b toward the inner face of the cover member 1. The holding members 3a, 3b and the support arm 2 are held and fixed by the fixing member 4 and the inner face of the cover member 1.