The present invention relates to a method and apparatus for performing communications by adjusting a resource unit. Efficient allocation of resource units can minimize power consumption. The minimization of power consumption brings about great advantages to M2M (machine-to-machine) communication. A terminal can transmit or receive data via different resource units. In this case, the resource units can be determined by MS. That is, some MS may use a particular resource unit, while the others may use a different resource unit. When different resource units are given, corresponding radio resource regions are also determined differently from one another. However, the total number of tones corresponding to the resource units may be the same.