A radio apparatus includes a first receiver that is a processing unit for amplifying and frequency converting a radio signal received via an antenna, thereby outputting an IF signal; a detector unit for detecting a preamble signal from the IF signal; a second receiver for amplifying and quadrature demodulating the radio signal, thereby generating an I-signal and a Q-signal; a demodulator unit for demodulating the I-signal and Q-signal to generate a data signal; and a control unit for halting the operation of the first receiver and further activating the second receiver when the detector unit detects the preamble signal and for activating the first receiver and halting the operation of the second receiver when the demodulator unit completes the demodulation of the I-signal and Q-signal.