A MIMO radar signal processing device comprising: a plurality of transmission signal generating units (111 1 -111 N) configured to generate transmission signals different from each other and configured to output the generated transmission signals to corresponding transmission antennas (1 1 -1 N); a plurality of matched filter banks (121 1 -121 M), each configured to receive a reception signal from a reception antenna (2 1 -2 M) corresponding to each of a plurality of reception antennas (2 1 -2 M) that capture reflected waves obtained by transmission waves transmitted from the transmission antennas (1 1 -1 N), reaching an object and being reflected as arrival waves, and configured to receive transmission signals from the plurality of transmission signal generating units (111 1 -111 N), and configured to output matched filter outputs serving as vector elements of reception signal vectors, using the transmission signals from the plurality of transmission signal generating units (111 1 -111 N) as a replica of a matched filter; characterized by a bidirectional angle measuring unit configured to obtain a bidirectional measured angle value constituted by a direction-of-departure and a direction-of-arrival in a reception signal vector of interest corresponding to a range Doppler cell given in target detection processing among reception signal vectors for matched filter outputs from the plurality of matched filter banks (121 1 -121 M); and a propagation mode distinguishing unit configured to distinguish, by the bidirectional measured angle value, whether a propagation mode of the reception signal vector of interest for the bidirectional measured angle value calculated by the bidirectional angle measuring unit is a direct propagation mode or a multipath propagation mode. a plurality of transmission signal generating units (111 1 -111 N) configured to generate transmission signals different from each other and configured to output the generated transmission signals to corresponding transmission antennas (1 1 -1 N); a plurality of matched filter banks (121 1 -121 M), each configured to receive a reception signal from a reception antenna (2 1 -2 M) corresponding to each of a plurality of reception antennas (2 1 -2 M) that capture reflected waves obtained by transmission waves transmitted from the transmission antennas (1 1 -1 N), reaching an object and being reflected as arrival waves, and configured to receive transmission signals from the plurality of transmission signal generating units (111 1 -111 N), and configured to output matched filter outputs serving as vector elements of reception signal vectors, using the transmission signals from the plurality of transmission signal generating units (111 1 -111 N) as a replica of a matched filter; characterized by a bidirectional angle measuring unit configured to obtain a bidirectional measured angle value constituted by a direction-of-departure and a direction-of-arrival in a reception signal vector of interest corresponding to a range Doppler cell given in target detection processing among reception signal vectors for matched filter outputs from the plurality of matched filter banks (121 1 -121 M); and a propagation mode distinguishing unit configured to distinguish, by the bidirectional measured angle value, whether a propagation mode of the reception signal vector of interest for the bidirectional measured angle value calculated by the bidirectional angle measuring unit is a direct propagation mode or a multipath propagation mode.