A transmission device includes a differential encoding section for differentially encoding transmission data, a first waveform generation section, a second waveform generation section, and two transmission antennas. A reception device includes a reception antenna, a delay detection section, and a data determination section for low-pass filtering a delay detection signal. The reception device receives modulated signals modulated by using two waveforms having low correlations with each other. Thus, regardless of the presence or absence of delay dispersion in a propagation path and even in a high-speed fading in which the propagation path varies at high speed, a transmission diversity effect can be achieved, thereby making it possible to improve transmission characteristics.