Various embodiments of the disclosure relate to an electronic device including a capacitive structure. The electronic device may include: a housing including a first plate, a second plate facing a direction opposite the first plate, and a side member comprising a side wall surrounding a space between the first plate and the second plate, the side member including a conductive portion; a conductive mid-plate disposed in the housing parallel to the second plate; a dielectric gap formed between the conductive portion and the conductive mid-plate; a printed circuit board (PCB) disposed inside the housing between the conductive mid-plate and the second plate, the PCB including a ground plane; and a capacitive structure comprising a conductive material disposed at a boundary portion of the dielectric gap and the conductive mid-plate between the conductive mid-plate and the PCB, the capacitive structure including a first conductive layer connected to the conductive mid-plate, a second conductive layer spaced apart from the first conductive layer and electrically connected to the ground plane, and a dielectric layer interposed between the first conductive layer and the second conductive layer.