In an equalizer arranged in a wireless communication device: information on correlation in one or more first wireless signals is generated; a channel vector is generated on the basis of the one or more first wireless signals; an extended, circulant matrix is generated; an extended channel vector is generated, the number of which is identical to the number of rows of the extended correlation matrix; and weight coefficients are calculated as a solution, in the frequency domain, of an equation expressed by the extended correlation matrix and the extended channel vector.