1. A propagation time measurement device that measures a propagation time of a transmission signal from when the transmission signal is transmitted, through wireless communication, from a base station to a terminal to when the transmission signal is returned to the base station from the terminal, wherein a plurality of continuous waves having different frequencies are combined to generate the transmission signal, the propagation time measurement device comprising: a correlation computation unit that generates a plurality of correlation values by performing a correlation computation on each of the continuous waves and a reception signal that is returned from the terminal and received by the base station; and a propagation time measurement unit that measures the propagation time from a phase of the correlation value generated for each continuous wave in the correlation computation.