A self-locking keyboard bracket is disclosed to include a four-bar linkage, formed of a base frame, a connecting frame, a coupling frame, and a braking mechanism, a supporting frame fastened pivotally with the coupling frame, and an angle adjustment control unit for locking the supporting frame to the coupling frame at the desired angle by means of the operation of a locking bar with a cam. The braking mechanism uses a beveled block to mach with a beveled guide block to further control friction resistance between the base frame and the connecting frame, thereby achieving self-locking of the keyboard bracket.