Disclosed herein is a demodulating device including, first high-frequency receiving means and second high-frequency receiving means for receiving a high-frequency signal of one of a first frequency and a second frequency, first signal strength detecting means and second signal strength detecting means for detecting strengths of signals received by the first high-frequency receiving means and the second high-frequency receiving means, respectively, and strength determining means for performing control so as to make the second high-frequency receiving means receive a high-frequency signal of the first frequency when the first high-frequency receiving means is made to receive the high-frequency signal of the first frequency and the second high-frequency receiving means is made to receive a high-frequency signal of the second frequency and when the second signal strength detecting means does not detect a predetermined signal strength within a predetermined time after the first signal strength detecting means detects a predetermined signal strength.