A computer case includes a chassis and at least one side plate. The chassis includes a base plate, an upper frame corresponding to the base plate, and two side frames connected to the base plate and the upper frame. Each of the side frames forms an opening. The base plate includes a hook portion bent inwardly adjacent to one side of the opening. At least one side plate is assembled to one of the two side frames and covers the opening. The at least one side plate includes a clasp member disposed protrudingly. The clasp member is movable with respect to the hook portion and engages with the hook portion, thereby allowing the other end of the at least one side plate, opposite to the clasp member, to open to form an open angle with respect to the upper frame.