A subarray spatial averaging unit performs spatial averaging of correlation matrices by dividing a received signal of an array antenna to a plurality of subarrays having different shapes, and calculating these correlation matrices for the respective subarrays having different shapes. An eigenvalue expanding unit performs eigenvalue expansion of correlation matrices for the respective plurality of subarrays having different shapes after spatial averaging. A wave count estimating unit estimates an incoming wave count by integrating eigenvalues of the plurality of subarrays having different shapes obtained by the eigenvalue expanding unit.