Electronic device having waterproof structure

An electronic device comprising:

• a front plate;
• a back plate facing a direction opposite to the front plate;
• a side member surrounding a space between the front plate and the back plate, constructed integrally with respect to the back plate, or bonded to the back plate, wherein the side member comprises:
• an outer structure constructed of a first metallic material and comprising at least one first surface constructing an outer surface of the side member and at least one second surface facing the space, and
• an inner structure constructed of a second metallic material different from the first metallic material and comprising at least one third surface at least partially in contact with the second surface and at least one fourth surface facing the space,
• wherein the inner structure is entirely disposed inside the space without being exposed to outside of the electronic device, and partially surrounded by the outer structure on three sides;
• a touch screen display exposed through the front plate;
• an internal structure disposed to the space so as to be adjacent to the side member, constructed of a first polymer material, and comprising at least one fifth surface at least partially in contact with the second surface;
• a wireless communication circuit electrically coupled with a portion of the inner structure;
• and
• a sealant disposed between the fourth surface and at least one sixth surface of the internal structure.