A moisture-proofing mobile device which is formed with a variously colored silicon skin, through dual injection molding, integrally over a region that includes an engagement part of the bottom casing with the top casing, clamping screw holes, and a battery mounting part, which may selectively include an antenna part, a camera part or a button part is provided. In accordance with the disclosed embodiments, there is no concern about malfunction or trouble of the mobile device even when the mobile device is used in a humid place, such as a kitchen, a bathroom, a swimming pool or a waterside, and the mobile device may provide a smooth and excellent grip feeling of a non-slip property, and may exhibit an improved impact resistance.