A handheld electronic device is provided. The handheld electronic device includes a front cover forming the front of the handheld electronic device, a back cover forming the back of the handheld electronic device, a side member at least partially surrounding a space between the front cover and the back cover, a display module, housed in the space, with a screen area exposed through the front cover, and a ground plate housed in the space. At least part of the side member and/or the back cover includes a conductive material. The handheld electronic device includes first and second connection terminals electrically connected to the at least part. The at least part forms at least part of an antenna of the handheld electronic device, and comprises first and second areas which are spaced apart from each other. The first area is electrically connected to the second area and the first connection terminal.