A radar module includes a high-frequency signal generator (10) comprising upper (1) and lower (2) parallel conductive plates, at least one dielectric rod (21) held between the parallel conductive plates (12), a metal diode mount (DM) held between the parallel conductive plates, a gunn diode member (GD) mounted on a side of the diode mount (DM), and a printed-circuit board (PB) mounted on the side of the diode mount (DM) in covering relationship to the gunn diode member (GD) and having a bias supply circuit (B1,B2) on its surface for supplying a bias voltage to the gunn diode member (GD). One terminal (7) of the gunn diode member (GD) extends through a through hole (H) defined in the printed-circuit board (PB), is exposed in the vicinity of the surface of the diode mount (GM), and is connected to the bias supply circuit. The printed-circuit board (PB) has a rectangular metal pattern (MP) dimensionally adjustable for adjusting the oscillation frequency of the gunn diode member (GD), and a varactor diode (VD) for modulating the frequency of a signal generated by the gunn diode member (GD) so that the high-frequency signal generator (10) can function as an FM signal generator.