A bracket device adapted to a slide rail mechanism is disclosed. The bracket device includes a first supporting frame, a second supporting frame and a bracket. The second supporting frame is movable relative to the first supporting frame. The bracket includes a side wall and at least one mounting member arranged adjacent to the side wall. Herein, the first supporting frame and the second supporting frame are able to be engaged with each other through a first structure and a second structure, in order to be moved simultaneously from a first position along a direction.