A system comprising: an electronic device upper surface; a rear surface opposite to the upper surface; a touch screen arranged on the electronic device upper surface; an exterior cover arranged on the rear surface; and an auxiliary device which is attached to or detached from the exterior cover by means of a coupling structure, wherein: the auxiliary device is coupled in close contact with at least a part of the touch screen, and is configured to operate the touch screen by a pressing operation, the auxiliary device causes a change in a capacitance value that is recognized by the electronic device by the pressing operation, the auxiliary device comprises a substrate arranged in close contact with the touch screen, and a keypad arranged on the substrate and provided with a plurality of key tops for inputting data by the pressing operation, the substrate comprises a first surface, and a second surface opposite to the first surface, the first surface comprises a non-conductive layer area, and first and second conductive layer areas which are divided by the non-conductive layer area and are isolated from each other, the second surface has a plurality of conductive pads formed thereon, and each of the conductive pads is electrically connected to the first conductive layer area through at least one connector and is in close contact with the touch screen, each of the connectors is formed by forming a via hole in the substrate and plating or filling the via hole, and each of the conductive pads is formed on a position corresponding to an intersection of a receiver and a transmitter which form the touch screen, such that there is one such intersection per one key top. an electronic device upper surface; a rear surface opposite to the upper surface; a touch screen arranged on the electronic device upper surface; an exterior cover arranged on the rear surface; and an auxiliary device which is attached to or detached from the exterior cover by means of a coupling structure, wherein: the auxiliary device is coupled in close contact with at least a part of the touch screen, and is configured to operate the touch screen by a pressing operation, the auxiliary device causes a change in a capacitance value that is recognized by the electronic device by the pressing operation, the auxiliary device comprises a substrate arranged in close contact with the touch screen, and a keypad arranged on the substrate and provided with a plurality of key tops for inputting data by the pressing operation, the substrate comprises a first surface, and a second surface opposite to the first surface, the first surface comprises a non-conductive layer area, and first and second conductive layer areas which are divided by the non-conductive layer area and are isolated from each other, the second surface has a plurality of conductive pads formed thereon, and each of the conductive pads is electrically connected to the first conductive layer area through at least one connector and is in close contact with the touch screen, each of the connectors is formed by forming a via hole in the substrate and plating or filling the via hole, and each of the conductive pads is formed on a position corresponding to an intersection of a receiver and a transmitter which form the touch screen, such that there is one such intersection per one key top. the auxiliary device is coupled in close contact with at least a part of the touch screen, and is configured to operate the touch screen by a pressing operation, the auxiliary device causes a change in a capacitance value that is recognized by the electronic device by the pressing operation, the auxiliary device comprises a substrate arranged in close contact with the touch screen, and a keypad arranged on the substrate and provided with a plurality of key tops for inputting data by the pressing operation, the substrate comprises a first surface, and a second surface opposite to the first surface, the first surface comprises a non-conductive layer area, and first and second conductive layer areas which are divided by the non-conductive layer area and are isolated from each other, the second surface has a plurality of conductive pads formed thereon, and each of the conductive pads is electrically connected to the first conductive layer area through at least one connector and is in close contact with the touch screen, each of the connectors is formed by forming a via hole in the substrate and plating or filling the via hole, and each of the conductive pads is formed on a position corresponding to an intersection of a receiver and a transmitter which form the touch screen, such that there is one such intersection per one key top.