Collapsible mobile radio device

The invention is to improve antenna performance in an internal antenna in a closed state without deteriorating the antenna performance in a state where a foldable portable radio apparatus is opened. A foldable portable radio apparatus includes a foldable mechanism in which an upper casing and a lower casing are rotatably connected, a first conductor plate and a second conductor plate that are provided in the upper casing , and a feeding system that is provided in the lower casing , and connects an antenna element , a circuit board , the first conductor plate , and the circuit board, a detecting unit that detects opened and closed states between the upper casing and the lower casing , and a first switching unit that switches between an electrically opened state and an electrically short-circuited state between the first conductor plate and the second conductor plate according to the detected result by the detecting unit