Radio communication system includes radio transmitter containing unit dividing transmission data into first-code blocks each having N-bit data, unit adding error detection codes to first-code blocks, unit assigning first-code blocks to second-code blocks each including M carriers each having L symbols, and unit transmitting second-code blocks, and radio receiver containing unit receiving second-code blocks, unit converting second-code blocks into first-code blocks, based on values of M and L, unit subjecting first-coded blocks to error correction decoding, unit detecting error of code block of first-code blocks subjected to error correction decoding, unit generating retransmission-request signal for requesting retransmission of code block including error, if error is detected, and unit transmitting retransmission-request signal, and radio transmitter further containing unit receiving retransmission-request signal from radio receiver, unit counting number of times of reception of retransmission-request signal, and unit changing values of M and L in accordance with counted number.