The present invention aims to provide a transmitter, a receiver and a radio communication method capable of preventing any increase in overhead due to insertion of reference signals without deteriorating the channel estimation accuracy. The radio communication method is provided for mapping reference signals to radio resources of a plurality of layers and transmitting the reference signals, having the steps of: generating the reference signals; oversampling the reference signals; and mapping the oversampled reference signals to resource elements of the layers respectively. Reference signals to be mapped to different layers are subjected to frequency division multiplexing in resource elements of same time and frequency domains.