To provide a transmitter of OFDMA transmission system which can enhance the transmission characteristics by optimizing the combination of resource blocks.

The transmitter further comprises: resource block selection means for outputting a plurality of resource blocks generated from a plurality of subcarriers simultaneously; precoding means for outputting a plurality of transmission streams; MCS determination means for determining a common MCS (Modulation and Coding Scheme) value for all resource blocks of each transmission stream; and difference calculation means for calculating the differential value of the MCS value and the common MCS value of the resource block for each resource block. The resource block selection means outputs a resource block having the maximum differential value and a resource block having the minimum differential value, out of a plurality of differential values, simultaneously as a set, and repeats the processing until all resource blocks are output.