In the foldable mobile radio apparatus constructed by coupling two cases to open and close, the high antenna performance can be secured over the wider band with the simple structure. A foldable mobile radio apparatus, includes a first case, an antenna element provided to the first case, a second case, a hinge portion for joining the first case and the second case turnably, a circuit board provided to an inside of the second case and having a ground pattern, and a feeding portion connected to a radio circuit on the circuit board. The hinge portion is formed of a nonconductive resin, and has a rotation shaft made of conductive metal to join the first case and the second case turnably. The rotation shaft is spatially coupled to the antenna element at a predetermined interval, and the rotation shaft is arranged to separate from the ground pattern on the circuit board, and is connected electrically to the feeding portion. Also, the antenna element, the rotation shaft, and the ground pattern on the circuit board operate as an antenna.