A bracket device adapted to mount a slide rail to a rack , the bracket device comprising: a bracket coupled with the slide rail and configured to mount the slide rail to the rack , the bracket comprising a side wall and at least one mounting member adjacent to the side wall ; and a fastening member pivoted to the bracket by a shaft member and configured to lock the rack at a locked position (P1), wherein when the fastening member is located at a position, a fastening portion of the fastening member is adjacent to the at least one mounting member ; when the fastening member is not located at the position, the fastening portion of the fastening member is away from the at least one mounting member ; wherein the bracket comprises two protruded lugs , the at least one protruded lug has a guiding feature , the guiding feature is an elongated hole and oriented identically to a length direction of the slide rail , such that the fastening member is movable relative to the bracket along the length direction of the slide rail , the fastening member is mounted to the guiding feature by the shaft member being disposed through a portion of the guiding feature ; characterized in that the bracket comprises a first structure arranged next to the two protruded lugs along the length direction of the slide rail , and the fastening member comprises a second structure ; wherein when the fastening member is located at the locked position (P1), the second structure is constrained between the two protruding portions of the first structure , so as to be configured to prevent the fastening member from moving along an axis direction (X) of the shaft member by means of the second structure abutting between the two protruding portions of the first structure (42, 202 302) . a bracket coupled with the slide rail and configured to mount the slide rail to the rack , the bracket comprising a side wall and at least one mounting member adjacent to the side wall ; and a fastening member pivoted to the bracket by a shaft member and configured to lock the rack at a locked position (P1), wherein when the fastening member is located at a position, a fastening portion of the fastening member is adjacent to the at least one mounting member ; when the fastening member is not located at the position, the fastening portion of the fastening member is away from the at least one mounting member ; wherein the bracket comprises two protruded lugs , the at least one protruded lug has a guiding feature , the guiding feature is an elongated hole and oriented identically to a length direction of the slide rail , such that the fastening member is movable relative to the bracket along the length direction of the slide rail , the fastening member is mounted to the guiding feature by the shaft member being disposed through a portion of the guiding feature ; characterized in that the bracket comprises a first structure arranged next to the two protruded lugs along the length direction of the slide rail , and the fastening member comprises a second structure ; wherein when the fastening member is located at the locked position (P1), the second structure is constrained between the two protruding portions of the first structure , so as to be configured to prevent the fastening member from moving along an axis direction (X) of the shaft member by means of the second structure abutting between the two protruding portions of the first structure (42, 202 302) . <EOS>