An OAM multiplexing communication system configured to subject a plurality of signal sequences to multiplex transmission by using an orbital angular momentum, OAM, mode as a base in a rotational direction dimension, the OAM multiplexing communication system comprising: a transmitting station including a transmitting antenna comprising an M-UCA formed of a plurality of uniform circular arrays, UCAs, that are concentrically disposed, each of the UCAs having a plurality of antenna elements disposed circularly at an equal interval, and a unit configured to perform basis transformation multiplying the transmitting weight in the diameter direction dimension in a polar coordinate system having a center of the plurality of UCAs as an origin, to perform basis transformation in the rotational direction dimension, and to subject the plurality of signal sequences to multiplex transmission for each complex mode formed by a combination of different bases in each dimension; and a receiving station including a receiving antenna comprising an M-UCA formed of a plurality of UCAs that are concentrically disposed, and a unit configured to receive a signal subjected to multiplex transmission from the transmitting station, to perform basis transformation in the rotational direction dimension, to perform basis transformation in multiplying the receiving weight in the diameter direction dimension, and to demultiplex the plurality of signal sequences subjected to the multiplex transmission. a transmitting station including a transmitting antenna comprising an M-UCA formed of a plurality of uniform circular arrays, UCAs, that are concentrically disposed, each of the UCAs having a plurality of antenna elements disposed circularly at an equal interval, and a unit configured to perform basis transformation multiplying the transmitting weight in the diameter direction dimension in a polar coordinate system having a center of the plurality of UCAs as an origin, to perform basis transformation in the rotational direction dimension, and to subject the plurality of signal sequences to multiplex transmission for each complex mode formed by a combination of different bases in each dimension; and a transmitting antenna comprising an M-UCA formed of a plurality of uniform circular arrays, UCAs, that are concentrically disposed, each of the UCAs having a plurality of antenna elements disposed circularly at an equal interval, and a unit configured to perform basis transformation multiplying the transmitting weight in the diameter direction dimension in a polar coordinate system having a center of the plurality of UCAs as an origin, to perform basis transformation in the rotational direction dimension, and to subject the plurality of signal sequences to multiplex transmission for each complex mode formed by a combination of different bases in each dimension; and a receiving station including a receiving antenna comprising an M-UCA formed of a plurality of UCAs that are concentrically disposed, and a unit configured to receive a signal subjected to multiplex transmission from the transmitting station, to perform basis transformation in the rotational direction dimension, to perform basis transformation in multiplying the receiving weight in the diameter direction dimension, and to demultiplex the plurality of signal sequences subjected to the multiplex transmission. a receiving antenna comprising an M-UCA formed of a plurality of UCAs that are concentrically disposed, and a unit configured to receive a signal subjected to multiplex transmission from the transmitting station, to perform basis transformation in the rotational direction dimension, to perform basis transformation in multiplying the receiving weight in the diameter direction dimension, and to demultiplex the plurality of signal sequences subjected to the multiplex transmission.