To provide a radio wave arrival direction estimator for reducing a calculation load by using a reduced number of antenna elements in a propagation environment where a multipath exists to estimate a radio wave arrival direction with high accuracy, and to provide an array antenna system using the same.

This estimator comprises: extraction means 321 to 32m for extracting a pilot signal from each of signals, obtained by quadrature-demodulating signals received by a plurality of systems of antenna elements and by converting them into a frequency region; correction means 381 to 38m for correcting IQ coordinates for pilot signals of a plurality of systems; cross correlation means 581 to 58m for finding cross correlation between each of time domain signals into which corrected pilot signals of the respective systems are converted and a time domain signal into which a reference pilot signal is converted; and a steering vector generation means 62 for generating steering vectors having, as factors, cross correlation values of the respective systems to indicate the direction of a desired wave.