An antenna device of a portable device such as a smartphone includes a connecting member having a conductive case and mounted on a circuit board of the portable device in a manner such that the case is connected to a ground surface of the circuit board; a radiator spaced from the circuit board; and at least one connecting pin provided between the case and the radiator. The radiator is connected to the ground surface through the connecting pin and the case. The antenna device advantageously may be easily installed in the internal space of a miniaturized, lightened and/or slimmed portable device by practically using a conductive component, e.g., the case, of the connecting member.