A case assembly for electronic appliance includes a first case having a plurality of engaging members and each engaging member includes two clamping protrusions. Each clamping protrusion includes a supporting portion and a protruding portion. A space is defined between the two clamping protrusions. A second case includes multiple ports and each port has a shoulder defined in an inside thereof and the shoulder is located corresponding to the protruding portions of the clamping protrusions. Multiple positioning members each have an insertion portion and a head. A transverse width of the opening of the space is smaller than a width of the insertion portion. When the insertion portion of each of the positioning members is inserted into the space corresponding thereto, the clamping protrusions are expanded outward by the positioning member, and the protruding portions are engaged on the shoulder of the second case.