Abstract: A code-division multiplex communication apparatus for carrying out multiplex communication by using pseudo noise (PN) codes and an application system thereof are provided, which have high SN ratio and can be used in an environment wherein feeble radio waves are to be received or the strength of output radio waves is regulated. Exclusive-OR circuits output exclusive ORs each based on data and a PN code associated with the corresponding channel, and a majority logic circuit performs a majority logic operation on the exclusive ORs. Namely, the majority logic circuit outputs a logical "1" or "0" that is greater in number. The majority logic output is subjected to phase modulation and is then transmitted as a transmission signal. The transmission signal is demodulated at a receiving side, based on the same PN codes as those used at the transmitting side, thereby demodulating the data. The code-division multiplex communication apparatus is applicable to radio LAN and FA system.