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 (17v, 17h) 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 (17v, 17h), and makes a ratio of a signal level of the calibration signal input to the respective channels (17v, 17h) to a signal level of the calibration signal having been amplified by the respective channels (17v, 17h) be consistent between the two channels (17v, 17h). 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 (17v, 17h) 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 (17v, 17h), and makes a ratio of a signal level of the calibration signal input to the respective channels (17v, 17h) to a signal level of the calibration signal having been amplified by the respective channels (17v, 17h) be consistent between the two channels (17v, 17h).