A composite circuit board includes a flexible board, rigid boards, adhesive layers, and protection glue; the adhesive layers are sandwiched between the rigid boards and the flexible board and used for bonding the rigid boards and the flexible board; the rigid boards are provided with step slots passing through the rigid boards; the adhesive layers are provided with through slots passing through the adhesive layers; the step slots and the through slots are communicated with each other to form a thinning recess; the thinning recess exposes the flexible board; and the protection glue covers steps of the thinning recess and at least a portion of the exposed area of the flexible board.