A communication apparatus includes: a switching device which modulates at least one of a first signal with a first frequency and passed through a first communication device and a second signal not passed through the first communication device at a second frequency lower than the first frequency; a signal combiner which combines together the first and second signals, at least one of which is modulated, to generate a composite signal containing a switching frequency component with an amplitude in response to the phase difference between the first and second signals at the second frequency; and a control unit which, based on the switching frequency component, obtains as a reference phase adjustment amount a phase adjustment amount applied by a phase adjuster in the first communication device.
