A radio station equipped with an array antenna, when transmitting an information symbol sequence to a particular radio station, uses a plurality of vectors, which are produced based on a propagation channel characteristic established between these radio stations, to simultaneously transmit a plurality of symbol sequences, which include the information symbol sequence, by way of vector multiplexing, thereby causing the particular radio station to receive the information symbol sequence, while causing other radio stations of different propagation channels to simultaneously receive a part or all the plurality of symbol sequences. Thus, when data is transmitted to a particular radio station via a radio communication channel, the concealment of information can be secured with a high level of security.