A temperature detection device includes: a detection processing unit configured to transmit a transmission radio wave, simultaneously receive a response radio wave corresponding to the transmission radio wave, and detect whether a temperature of an object to be measured is normal or abnormal based on the response radio wave; and a temperature sensing unit configured to receive the transmission radio wave and transmit the response radio wave responding to the transmission radio wave. The detection processing unit calculates, from the response radio wave received via a second antenna, an amplitude, a phase, or a quadrature phase amplitude of the response radio wave and compares the temperature of the object to be measured to a temperature determined in advance based on a result of the calculation.