An electronic device comprising: a housing including: a front plate, a rear plate disposed opposite the front plate, and a lateral member surrounding a space between the front plate and the rear plate and including a conductive portion and a non-conductive portion; and an antenna module disposed in the space and including: a printed circuit board having a first surface disposed to face the lateral member in the space, and a second surface disposed opposite the first surface, and at least one antenna element disposed on the first surface or near the first surface in the printed circuit board, and configured to form a beam pattern toward the lateral member, wherein the conductive portion includes, when viewed toward the first surface, a notch having a recessed shape in a direction from the rear plate to the front plate, wherein the non-conductive portion is disposed at least partially in the notch and faces the at least one antenna element, wherein the notch has a third surface facing the rear plate, characterised in that the conductive portion includes at least one protrusion extended from a part of the third surface toward the rear plate and spaced apart from the first surface in a direction that the first surface faces, wherein, when viewed toward the first surface, the at least one protrusion does not overlap the at least one antenna element, and wherein, when viewed toward the first surface, the at least one protrusion comprises a fourth surface, a fifth surface, and a sixth surface, the fourth surface facing the rear plate, and the fifth surface and the sixth surface connecting the fourth surface and the third surface and disposed opposite to each other. a housing including: a front plate, a rear plate disposed opposite the front plate, and a lateral member surrounding a space between the front plate and the rear plate and including a conductive portion and a non-conductive portion; and a front plate, a rear plate disposed opposite the front plate, and a lateral member surrounding a space between the front plate and the rear plate and including a conductive portion and a non-conductive portion; and an antenna module disposed in the space and including: a printed circuit board having a first surface disposed to face the lateral member in the space, and a second surface disposed opposite the first surface, and at least one antenna element disposed on the first surface or near the first surface in the printed circuit board, and configured to form a beam pattern toward the lateral member, a printed circuit board having a first surface disposed to face the lateral member in the space, and a second surface disposed opposite the first surface, and at least one antenna element disposed on the first surface or near the first surface in the printed circuit board, and configured to form a beam pattern toward the lateral member, wherein the conductive portion includes, when viewed toward the first surface, a notch having a recessed shape in a direction from the rear plate to the front plate, wherein the non-conductive portion is disposed at least partially in the notch and faces the at least one antenna element, wherein the notch has a third surface facing the rear plate, characterised in that the conductive portion includes at least one protrusion extended from a part of the third surface toward the rear plate and spaced apart from the first surface in a direction that the first surface faces, wherein, when viewed toward the first surface, the at least one protrusion does not overlap the at least one antenna element, and wherein, when viewed toward the first surface, the at least one protrusion comprises a fourth surface, a fifth surface, and a sixth surface, the fourth surface facing the rear plate, and the fifth surface and the sixth surface connecting the fourth surface and the third surface and disposed opposite to each other.