Chair back adjusting device

The utility model provides a chair back adjusting device. The chair back adjusting device comprises a chair back frame and a chair back connecting frame, a first rotating part is arranged on the chair back frame; a second rotating part is arranged on the chair back connecting frame, and the first rotating part and the second rotating part are movably connected through an adjusting assembly; a first limiting part of which the peripheral wall is of a non-circular structure is arranged on the adjusting assembly, and the second rotating part is connected with the first limiting part in a limiting manner; the first rotating part is provided with a special-shaped first limiting hole, the first limiting part is installed in the first limiting hole in a clamped mode, the first limiting part can at least conduct two-stage rotating adjustment in the first limiting hole, and the position of the first limiting part in the first limiting hole is adjusted so as to adjust the distance between the chair back frame and the ch