A radar device , comprising: a transmission signal generation part which repeatedly generates, at a time interval, a transmission signal to be output to an antenna in order to transmit a detection signal from the antenna ; a frequency conversion part which converts a frequency of an echo signal obtained by reflecting the detection signal and receiving the detection signal by the antenna , and amplifies a signal level thereof, within a period from a time when the transmission signal generation part completes outputting the transmission signal to the antenna to a time when a next one of the transmission signal starts to be output to the antenna ; a signal processing part which processes and outputs a signal input from the frequency conversion part ; a path switching part which outputs the transmission signal output by the transmission signal generation part to the frequency conversion part as a calibration signal at a timing while the transmission signal is being output to the antenna ; and an amplification gain changing part which changes an amplification gain of the frequency conversion part based on a signal level of the calibration signal input to the frequency conversion part and a signal level of the calibration signal having been amplified by the frequency conversion part , characterised in that the frequency conversion part has two channels which frequency-convert two polarized waves orthogonal to each other and amplify signal levels thereof, respectively, and the amplification gain changing part changes amplification gains of the respective channels , and makes a ratio of a signal level of the calibration signal input to the respective channels to a signal level of the calibration signal having been amplified by the respective channels be consistent between the two channels . a transmission signal generation part which repeatedly generates, at a time interval, a transmission signal to be output to an antenna in order to transmit a detection signal from the antenna ; a frequency conversion part which converts a frequency of an echo signal obtained by reflecting the detection signal and receiving the detection signal by the antenna , and amplifies a signal level thereof, within a period from a time when the transmission signal generation part completes outputting the transmission signal to the antenna to a time when a next one of the transmission signal starts to be output to the antenna ; a signal processing part which processes and outputs a signal input from the frequency conversion part ; a path switching part which outputs the transmission signal output by the transmission signal generation part to the frequency conversion part as a calibration signal at a timing while the transmission signal is being output to the antenna ; and an amplification gain changing part which changes an amplification gain of the frequency conversion part based on a signal level of the calibration signal input to the frequency conversion part and a signal level of the calibration signal having been amplified by the frequency conversion part , characterised in that the frequency conversion part has two channels which frequency-convert two polarized waves orthogonal to each other and amplify signal levels thereof, respectively, and the amplification gain changing part changes amplification gains of the respective channels , and makes a ratio of a signal level of the calibration signal input to the respective channels to a signal level of the calibration signal having been amplified by the respective channels be consistent between the two channels . <EOS>