To provide a radio LAN capable of attaining a high data transmission speed without suffering adverse influences of the interference in multiplex channels.

A data modulator 66 transforms input data into a Walsh function symbolic waveform, an exclusive OR logic gate 72 combines it with a pseudo noise from a pseudo noise generator 70 to transmit via an RF modulator. The Walsh function coding prolongs the duration time of symbols. While a high speed data transmission is conducted with the direct sequence spread spectrum modulation, it is possible to obtain a process gain enough to substantially solve the interference in multiple channels.