A combination cabinet includes a main body, a plurality of bottom boards, a plurality of back boards, a plurality of resting boards, a top board, and a connecting seat. Thus, the main body is folded to have a flat shape and all parts of the combination cabinet are folded and detached before assembly, so that the combination cabinet has a smaller volume, thereby facilitating packaging, storage and transportation of the combination cabinet. In addition, the combination cabinet is assembled and disassembled easily and quickly without needing aid of any hand tool, thereby facilitating a user assembling and disassembling the combination cabinet.