A bracket device includes a bracket, a fastening member and a resilient member. The bracket includes a longitudinal wall and at least one mounting member mounted adjacent thereto. The fastening member is longitudinally displaceable with respect to the bracket and includes a side wall and a fastening portion bent with respect to the side wall. The resilient member is for providing a resilient force to the bracket and the fastening member. The bracket is arranged with a first engaging feature, and the fastening member is arranged with a second engaging feature. When the fastening member displaces with respect to the bracket from a first position to a second position, the fastening portion is close to the at least one mounting member, and the first engaging feature is engaged with the second engaging feature, such that the fastening member is kept at the second position with respect to the bracket.