According to various embodiments, an electronic device includes a front plate, a rear plate facing away from the front plate, and a side member surrounding the space between the front plate and the rear plate. The side member comprises: a housing including a conductive annular member; at least one mounting member connected to the side member and detachably mounted to a portion of the human body such that the rear plate is configured to be oriented toward a portion of the human body; a substrate (PCB) disposed in parallel with the front plate in the space and including a ground plane; at least one wireless communication circuit disposed on the substrate; a first electrical path connected between the wireless communication circuit and a first point of the conductive annular member; and a second electrical path connected between the ground plane and a second point of the conductive annular member, wherein a first region of the conductive annular member defined between the first point and the second point has a first length, and a second region of the conductive annular member defined between the first point and the second point has a second length that is shorter than the first length, wherein the side member includes an extension part disposed in the space and extending along a first region of the annular member or a portion of the second region and may include a conductive pattern electrically connected to the wireless communication circuit. Various other embodiments may be possible. Various embodiments may be possible.