Disclosed is a power control method by a first device in a communication system. In the power control method, a first communication module is activated by supplying power to the first communication module without supplying power to the second communication module, data is received using the first communication module, the second communication module is activated by supplying power to the second communication module for transmitting the data to a second device using the second communication module, the data is transmitted to the second device using the second communication module, and the power supply to the second communication module is interrupted, if the data transmission is completed.