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