A communication apparatus (1; 2) comprising: a plurality of communication devices (11; 51) each of which transmits or receives a signal and each of which includes a phase adjuster (22; 64) for adjusting the phase of the signal; and an oscillator (10; 50) which supplies a first signal with a first frequency; and characterized by a switching device (14, 15; 40; 55) which modulates at least one of the first signal passed through a first communication device (11-1; 51-1) among the plurality of communication devices (11; 51) and a second signal with the first frequency but not passed through the first communication device (11-1; 51-1) at a second frequency lower than the first frequency; a signal combiner (13; 42, 43; 65) which combines together the first signal passed through the first communication device (11-1; 51-1) and the second signal, at least one of which is modulated, to generate a composite signal containing a switching frequency component with an amplitude in response to a phase difference taken between the first signal and the second signal at the second frequency; and a control unit (12; 52) which, based on the switching frequency component contained in the composite signal, obtains as a reference phase adjustment amount a phase adjustment amount applied by the phase adjuster (22; 64) in the first communication device (11-1; 51-1) when the phase difference between the first signal and the second signal is at a prescribed value, and which, based on the reference phase adjustment amount, controls the phase adjuster (22; 64) in the first communication device (11-1; 51-1) so that a predetermined phase difference is provided between the signal that the first communication device (11-1; 51-1) transmits or receives and the signal that a second communication device (11-2; 51-2) adjacent to the first communication device (11-1; 51-1) among the plurality of communication devices (11; 51) transmits or receives. a plurality of communication devices (11; 51) each of which transmits or receives a signal and each of which includes a phase adjuster (22; 64) for adjusting the phase of the signal; and an oscillator (10; 50) which supplies a first signal with a first frequency; and characterized by a switching device (14, 15; 40; 55) which modulates at least one of the first signal passed through a first communication device (11-1; 51-1) among the plurality of communication devices (11; 51) and a second signal with the first frequency but not passed through the first communication device (11-1; 51-1) at a second frequency lower than the first frequency; a signal combiner (13; 42, 43; 65) which combines together the first signal passed through the first communication device (11-1; 51-1) and the second signal, at least one of which is modulated, to generate a composite signal containing a switching frequency component with an amplitude in response to a phase difference taken between the first signal and the second signal at the second frequency; and a control unit (12; 52) which, based on the switching frequency component contained in the composite signal, obtains as a reference phase adjustment amount a phase adjustment amount applied by the phase adjuster (22; 64) in the first communication device (11-1; 51-1) when the phase difference between the first signal and the second signal is at a prescribed value, and which, based on the reference phase adjustment amount, controls the phase adjuster (22; 64) in the first communication device (11-1; 51-1) so that a predetermined phase difference is provided between the signal that the first communication device (11-1; 51-1) transmits or receives and the signal that a second communication device (11-2; 51-2) adjacent to the first communication device (11-1; 51-1) among the plurality of communication devices (11; 51) transmits or receives.