A radar module includes a high-frequency signal generator comprising upper and lower parallel conductive plates, at least one dielectric rod held between the parallel conductive plates, a metal diode mount held between the parallel conductive plates, a gunn diode member mounted on a side of the diode mount, and a printed-circuit board mounted on the side of the diode mount in covering relationship to the gunn diode member and having a bias supply circuit on its surface for supplying a bias voltage to the gunn diode member. One terminal of the gunn diode member extends through a through hole defined in the printed-circuit board, is exposed in the vicinity of the surface of the diode mount, and is connected to the bias supply circuit. The printed-circuit board has a rectangular metal pattern dimensionally adjustable for adjusting the oscillation frequency of the gunn diode member, and a varactor diode for modulating the frequency of a signal generated by the gunn diode member so that the high-frequency signal generator can function as an FM signal generator.