Abstract: In an radar apparatus according to the present invention, any change detected in the characteristic of a receiver circuit is corrected during normal operation or at the time of an initial adjustment before shipment from factory and, furthermore, any change occurring in the characteristic due to aging or temperature variations in the operating environment is corrected as needed. In the radar apparatus which includes a plurality of receiver circuit systems to correspond with a plurality of receiving antennas, channel signals ch1 and ch2 having the same characteristics are generated by the switching operation of a second switch from a received channel signal received by an antenna selected by a first switch, and the thus generated signals are input to the respective receiver circuit systems. Any change in characteristic is detected by comparing signal level and phase between the channel signals converted from analog to digital.