A pseudo-spatial-average-covariance-matrix generating unit selects, from matrixes Rf1, Rf2, Rb1 and Rb2, one appropriate matrix or two or more appropriate matrixes for combination to generate a pseudo-spatial-average-covariance matrix R. A pseudo-spatial-average-covariance-matrix Hermitian-conjugate product generating unit generates a target-count-estimation matrix RRH. A target-count-estimation-matrix decomposing unit performs LU decomposition on RRH into a lower triangular matrix L and an upper triangular matrix U. An index generating unit generates an index using elements of the upper triangular matrix U. An index-parameter scanning unit estimates a target count by using the index generated by the index generating unit.