A method for transmitting a preamble for legacy support is provided. In a communication system for supporting at least one of a first system corresponding to a legacy system and a second system which corresponds to an evolved system and supports two or more scalable bandwidths, a method for transmitting a preamble for the second system is provided. A preamble sequence is generated on the basis of a smallest bandwidth of the two or more scalable bandwidths, the generated preamble sequence is mapped to a resource zone to have a repetition factor which is relatively prime to a repetition factor of a repetition factor of a preamble for the first system, and the preamble sequence mapped to the resource zone is transmitted as the preamble for the second system.