An interleaving method to which time-first-mapping is applied for a plurality of channel-coded and rate-matched code blocks considering a modulation scheme in a mobile communication system is provided. The interleaving method includes determining sizes of a horizontal area and a vertical area of an interleaver memory, selecting a defined number of adjacent coded symbols in a same code block according to a modulation scheme, generating modulation groups in a vertical direction, sequentially writing the modulation groups in the horizontal area on a row-by-row basis, and sequentially reading the symbols written in the interleaver memory on a column-by-column basis.