A Doppler shift frequency measuring device is provided, which includes a plurality of transmitters respectively configured to transmit a transmission wave, a plurality of receivers provided corresponding to the transmitters, respectively, and configured to receive reception waves that are reflection waves caused by the transmission waves from the transmitters, respectively, and a reception signal processor configured to calculate Doppler shift frequencies of the reception waves by processing reception signals obtained based on the reception waves received by the receivers. The reception signal processor includes a reception circuit configured to generate a synthesized signal by synthesizing processing target signals of which center frequencies of main lobes of power spectra are different from each other, the processing target signals generated based on the reception waves, and a Doppler shift frequency calculating module configured to calculate the Doppler shift frequencies of the reception waves based on the synthesized signal.