An electronic device is provided, which includes a housing including a sidewall; a through-hole configured to penetrate the sidewall; an assembling hole formed adjacent to the through-hole inside the housing; a key assembly configured to be received in the assembling hole and disposed to face an inner surface of the housing in an area where the through-hole is positioned; and a fixing member configured to be received in the assembling hole and to bring a surface of the key assembly into close contact with the inner surface of the housing around the through-hole and seal between the through-hole and an inner space of the housing.