A method and apparatus for setting transmission power of a data channel by a mobile station in a Frequency Division Multiple Access (FDMA) system. The power setting method and apparatus includes receiving scheduling information from a base station; comparing a data rate of desired transmission data with a data rate of the scheduled data; if the data rate of desired transmission data is less than the data rate of the scheduled data, adjusting a currently set transmission power offset value according to the data rate of desired transmission data and the data rate of the scheduled data; and setting transmission power of the data to be transmitted to the base station using the adjusted transmission power offset value, and transmitting the data using the set transmission power value.