The invention determines a transmission power value or a data rate in transmission power control in a reception side apparatus. A communication apparatus includes a modulation class controlling portion for selecting one data rate, and transmits a communication signal having the selected one data rate to a communication apparatus. The communication apparatus includes a storage portion for storing necessary received power data, and a line quality calculating portion for acquiring received power data of the received communication signal, for acquiring transmission power remaining data representing a difference between a maximum transmittable power of the communication apparatus and a transmission power when the communication apparatus transmits the communication signal, and for determining a data rate based on maximum received power data estimated based on the transmission power remaining data and received power data, and necessary received power data, and transmits information on the data rate to the communication apparatus.