PURPOSE: To suppress the peak power of a transmitter in a time division multiplex digital radio communication system in which a multi-sub carrier QAM system is used and by which communication with plural slots dividing a digital signal by such modulation system is performed.

CONSTITUTION: When information symbols S0-Sf to be transmitted simultaneously in plural sub carriers are concentrated in adjacent signal space, the transmission of one information symbol is shifted later, and a specific symbol nearest to signal space opposite to the above concentrated signal space out of plural specific symbols P0-P3 that is the symbols different from the information symbols S0-Sf and which divide the range of signal space of 360° is transmitted instead of the information symbol. Therefore, since concentration to the adjacent information symbol can be prevent from occurring among the plural sub carriers, the transmitter in which the peak power can be decreased, and with high power efficiency and high profitability can be obtained.