In a radar image processing device and a radar image processing method which can accurately extract a change of a ground surface, a communication interface unit (10) obtains a plurality of radar image data of a same observation target obtained at different times and stores in a radar image storage unit (12), and a registration processor (14) reads the plurality of radar image data from the radar image storage unit (12) and registrates the radar image data with respect to each other. Then, a characteristic value calculating unit (18) calculates a plurality of characteristic values indicating a state of a ground surface which is the observation target based on the positioned radar image data. A change candidate region extracting unit (34) extracts change candidate regions for each of the characteristic values, and a judging unit (36) extracts a region of land cover change of the observation target from the change candidate regions using a threshold value, an extracting condition, and a judging function determined by a judgment method determining unit (24).