Provided is a displacement measurement device including: a radio wave transmitter installed at a measurement position, which is configured to transmit radio waves of a plurality of frequencies from a transmission antenna; and a radio wave receiver installed at a fixed position. The radio wave transmitter includes: a plurality of reception antennas each configured to output received signals indicating the results of receiving the radio waves of the plurality of frequencies; a relative phase combining unit configured to combine, for the plurality of frequencies, relative phases between the plurality of reception antennas; a relative phase shifting unit configured to shift the relative phase between the plurality of frequencies, which is combined by the relative phase combining unit; and a positioning calculation unit configured to calculate the positioning value of the transmission antenna based on the relative phase shifted by the relative phase shifting unit.