Provided is a technology for extending a guard interval for individual user equipment in an OFDMA system. The transmitting apparatus includes: a guard interval extension processor for generating symbols with a guard interval extended by copying a part of a current symbol and pasting the copied part to a last part of a previous symbol; a Fourier Transform (FT) processor for receiving the processed symbols from the guard interval extension processor and performing an FT process on the received processed symbols; an Inverse Fast Fourier Transform (IFFT) processor for performing an IFFT process on the FT processed symbols from the FT processor; a mapping processor for mapping outputs of the FT processor to input points of the IFFT processor to load the FT processed frequency-domain data on corresponding sub-carriers; and a cyclic prefix inserter for inserting a cyclic prefix code to output of the IFFT processor.