To measure the delay time of an incoming wave.

The inverse matrix Rex-1 of an auto-correlation matrix of QNd order reception baseband signal vector is obtained (43) from a delay reception baseband signal group which is composed by severally delaying in order the reception baseband signal group x1(i)-xQ(i) of terminals 251-25Q obtained from Q pieces of antenna reception signals as much as a sampling period T3 through shift registers 411-41Q, and in order to prescribe a restricting condition for keeping a delay time τ, the mean electric power of an incoming wave having an arrival angle θ fixed, a steering vector AexH (θ, τ) expanded by τ, θ is obtained (44), and its complex conjugate transpose AexH (θ, τ) is obtained (34), and Rex-1 is multiplied by AexH (θ, τ) (35), and an inner product between the product and AexH (θ, τ) is obtained, and its reciprocal is obtained and outputted to a terminal 38 (37), and τ and θ of A (θ, τ) are altered in order and the output of the terminal 38 is plotted to obtain θ and τ for producing a peak.