The data download method of a terminal device processing data downloaded in progressive download mode is provided. The method includes measuring bandwidth of the data downloaded, requesting, when the measured bandwidth is narrower than a reference bandwidth, for transmitting data with narrow bandwidth, registering a duration in which the data is downloaded with narrow bandwidth as a backup duration, requesting, when the measured bandwidth is equal to or greater than the reference bandwidth, for retransmission of backup data corresponding to the backup duration through a backup channel, and storing the data of the backup duration.