A computer measures amplitudes and phases respective received signals S60a relative to a transmitting signal when radio waves are radiated solely from each of the scatterer antennas and received by using a calibration receiving antenna, determines a target amplitude based on measured amplitudes, and determines a target phase based on measured phases. Reference attenuation amount control voltages for respective attenuators are set to attenuation amount control voltages for making the measured amplitudes coincidence with an identical target amplitude, and a reference phase shift amount control voltage for each phase shifter is set to phase shift amount control voltages for making the measured phases coincidence with an identical target phase.