A compact cellular phone with a foldable configuration and two planar antennas having outward directivities are provided inside the compact cellular phone in the foldable configuration. An interval between the two planar antennas provided to a pair of housings is equal to or wider than a width of a human palm in a state in which the compact cellular phone is open. The two planar antennas are planar inverse F-type antennas or patch antennas and impedance around each of the two planar antennas is measured. Then, one of the two planar antennas, which has a preferred transmission characteristic, is selected and used.