A method for reducing inter-cell interference (ICI) in a mobile communication system controls transmission signal power of an uplink signal from a terminal based on signal power measurement for a signal received from a base station of a neighboring cell. A terminal receives a signal from a base station of a neighboring cell via a wireless channel, measures a channel response against a threshold value across an applicable frequency band by using the received signal, determines a transmission signal power for each frequency band used for data transmission based on the measured channel response, and transmits data to a home cell base station according to the transmission signal power for each frequency band. The terminal may measure a channel response based on signals received from multiple base stations in multiple neighboring cells, and may also evaluate signal power of a signal transmitted from the home cell.