Adjusting device

The invention discloses an adjusting device which is used for being combined with a front-end element to form a head-mounted display device. The adjusting device comprises a shell, a first binding belt, a second binding belt and an adjusting module. The first binding belt is suitable for being fixed to one end of the front end element, and one part of the first binding belt is movably arranged inthe shell. The second binding belt is suitable for being fixed to the other end of the front end element, and one part of the second binding belt is movably arranged in the shell. The second binding belt partially overlaps the first binding belt. The adjusting module is arranged in the shell and coupled with the first binding belt and the second binding belt. When the shell moves along a direction, the shell is linked with the first binding belt and the second binding belt relative to the front end element so as to change the total length of the first binding belt and the second binding belt when the first binding bel