A direction finder is provided that can measure the incoming angles of plural incoming signals without spatially moving antenna elements and can be used in outdoor mobile communication environments. The direction finder also can shorten the measurement time. An array antenna comprises plural antenna elements arranged at regular intervals. The received signal components due to the mutual coupling between the antenna elements are removed by multiplying time series signal groups by the inverse matrix of a coupling coefficient matrix of the array antenna. The time series signal groups are obtained by modulating signals received with the array antenna. The covariance matrix of the received signal group can be subjected to a movement averaging process in terms of the Vandermonde format. The coupling coefficient matrix of the array antenna is obtained by normalizing the measurement result of an array element pattern containing a mutual coupling with a measurement result of an element pattern of a sole antenna element not containing a mutual coupling and then by expanding the normalized result in a Fourier series.