Reception signals received by first to fourth antennas 11 to 14 are sequentially selected one by one repeatedly in accordance with first to fourth switches 31 to 34 being controlled by first to fourth switch control circuits 41 to 44, respectively, so as to be inputted to a signal shaping section 60. The reception signals having been shaped by the signal shaping section 60 are sampled by a sample-and-hold section 71 and AD-converted by an AD converter 72 in accordance with a time at which the reception signals are sequentially selected. The resultant signals are converted into parallel signals by a serial-parallel conversion section 73. Thus, the parallel signals are obtained as the reception signals of the first to the fourth antennas 11 to 14.