A distance measuring apparatus, comprising: a transmitter that is adapted to transmit a request signal from an antenna to the outside via radio waves having three or more different carrier frequencies; a receiver that is adapted to receive a reflection signal which is obtained when the request signal transmitted from the transmitter is reflected by a reflector while being modulated; a phase information acquirer that is adapted to calculate a phase change amount between the reflection signal received by the receiver and the request signal for each of the carrier frequencies transmitted from the transmitter; and a distance calculator that is adapted to calculate a distance between the antenna and the reflector on the basis of the carrier frequencies and the phase change amount for each of the carrier frequencies acquired by the phase information acquirer, wherein: the distance measurement apparatus is adapted to receive the reflection signal from the reflector via three or more different carrier frequencies; and the receiver comprises a frequency converter that is adapted to convert the received reflection signal to an I signal and a Q signal; characterized in that: the phase information acquirer is adapted to: extract, for each of the carrier frequencies of the received reflection signal, one of the I signal and the Q signal that has the smaller signal level, and use the smaller one as a minimal component for that carrier frequency, select two carrier frequencies each having a minimal component of which the signal level is greater than that of at least one of the minimal components of the other carrier frequencies, and acquire the phase change amount for each of the selected two carrier frequencies. a transmitter that is adapted to transmit a request signal from an antenna to the outside via radio waves having three or more different carrier frequencies; a receiver that is adapted to receive a reflection signal which is obtained when the request signal transmitted from the transmitter is reflected by a reflector while being modulated; a phase information acquirer that is adapted to calculate a phase change amount between the reflection signal received by the receiver and the request signal for each of the carrier frequencies transmitted from the transmitter; and a distance calculator that is adapted to calculate a distance between the antenna and the reflector on the basis of the carrier frequencies and the phase change amount for each of the carrier frequencies acquired by the phase information acquirer, wherein: the distance measurement apparatus is adapted to receive the reflection signal from the reflector via three or more different carrier frequencies; and the receiver comprises a frequency converter that is adapted to convert the received reflection signal to an I signal and a Q signal; the phase information acquirer is adapted to: extract, for each of the carrier frequencies of the received reflection signal, one of the I signal and the Q signal that has the smaller signal level, and use the smaller one as a minimal component for that carrier frequency, select two carrier frequencies each having a minimal component of which the signal level is greater than that of at least one of the minimal components of the other carrier frequencies, and acquire the phase change amount for each of the selected two carrier frequencies.