A folding chair includes two standing posts, two diagonal bracing mechanisms, and a linkage mechanism, where the linkage mechanism includes two linkage posts that are crossed and hinged with each other. The diagonal bracing mechanisms each include two diagonal braces, two under-frame posts, a first connector, and a second connector. The upper ends of the two diagonal braces and an upper end of one linkage post are hinged with the first connector, and the lower ends of the two diagonal braces are respectively hinged with the first ends of the two under-frame posts. The second ends of the two under-frame posts and the lower end of the linkage post are hinged with the second connector. The two standing posts are respectively connected to two first connectors and respectively limit the positions of the two first connectors.