A signal transmission apparatus in a communication system, includes: a first IFFT unit for generating a first signal by performing inverse fast Fourier transform on a first communication service signal corresponding to a first communication scheme; a first CP inserter for generating a second signal by inserting a first cyclic prefix having a length corresponding to the first communication scheme into the first signal; a second IFFT unit for generating a third signal by performing inverse fast Fourier transform on a second communication service signal corresponding to a second communication scheme; a second cyclic prefix inserter for generating a fourth signal by inserting a second cyclic prefix having a length corresponding to the second communication scheme into the third signal; and a transmission unit for multiplexing the second signal and the fourth signal and transmitting the multiplexed signals.