In a sensor and a radar for measuring the distance and the moving speed of a target by radiating a radio frequency, particularly a millimeter wave, compatibility between cost reduction and high detection performance has been conventionally a significant problem. In the present invention, the frequency of a transmitted signal changes during a fixed time while performing digitally-frequency-modulation on frequency sweeping straight lines extending, with different slopes relative to the time axis, from plural slightly different initial values serving as starting points, the signal is transmitted after being modulated so as to periodically repeat the sweep time serving as a unit, signal components corresponding to the respective sweeping slopes are digitally sampled, in synchronization with the transmitted modulation signal, from a received signal which is reflected and returned from a target, and the received signal is analyzed.