An electronic device is provided that includes a housing; a printed circuit board including a first and second surfaces; an antenna module disposed on the first surface and adjacent to a side surface member, forming a first gap therewith, the antenna module being configured to radiate an antenna beam; a wireless communication circuit electrically connected with the antenna module, and configured to transmit or receive a signal having a frequency between 3 and 100 gigahertz; and a dielectric structure including a seating portion to have the antenna module mounted thereon, and configured to form the antenna beam to be radiated toward an outside of the housing.