An improved structure for portable electronic device is presented using elastic material for building guide rails for support, protecting a mini storage device inside the portable device, and permitting the consumer, while using the portable electronic device, to protect the mini storage device from shock damage. The portable electronic device contains a casing. The casing further contains a containing space. The containing space connects to the exterior via an opening. The parallel side walls of the containing space, which also include a pair of guide rails, are perpendicular to the exterior. The guide rails are made of an elastic material. The mini storage device passes through the above opening, enters the casing, moves along the guide rails, and finally is placed inside the containing space.