A bracket device includes a bracket and a fastening member. The fastening member is pivoted to the bracket by a shaft member. The bracket includes a first structure, and the fastening member includes a second structure. When the fastening member is located at a locked position, the second structure is in cooperation with the first structure, so as to prevent the fastening member from tilting relative to the bracket. One of the first structure and the second structure is a protruding portion, and the other one of the first structure and the second structure is a hole or a recessed portion.