In a radio reception apparatus compatible with adaptive modulation, based
on a received IQ signal processed by a reception processing unit, a
determining unit calculates EVM that corresponds to a magnitude of
shift-off between a true symbol point and the received symbol point. The
calculated EVM is averaged and thereafter applied to a control unit. The
control unit compares the applied EVM with a prescribed threshold value,
and determines with high accuracy, switching among a plurality of
modulation methods having different multi-value numbers.