A frame transmission method in a wireless communication system comprises setting a primary frame including a multiplicity of primary sub-frames, setting a secondary frame including a multiplicity of secondary sub-frames, and transmitting the secondary frame, wherein each of the primary sub-frames and each of the secondary sub-frames consists of multiple OFDM symbols, the OFDM symbols included in the primary sub-frame and the OFDM symbols included in the secondary sub-frame have different CP (Cyclic Prefix) lengths from one another, and the primary sub-frames and the secondary sub-frames are all equal in length. It is an advantage of the invention that frames consisting of OFDM symbols with different CP lengths can coexist together. Moreover, when each of the sub-frames within one frame consists of multiple OFDM symbols with different CP lengths, even the sub-frames can coexist together.