A foldable portable radio terminal is disclosed which normally optimizes an antenna characteristic by an antenna matching circuit even if the body length of the foldable portable radio terminal varies. A folded state detection circuit sends a detection signal to a control section depending upon whether or not the foldable portable radio terminal is folded. An antenna matching circuit is determined so that the antenna characteristic of an antenna is optimized when the foldable portable radio terminal is in a folded state. When the foldable portable radio terminal is unfolded, the control section renders a matching characteristic changeover circuit operative to change over the matching characteristic of the antenna matching circuit so that, even when the foldable portable radio terminal is in an unfolded state, the antenna characteristic by the antenna matching circuit may be optimized.