An apparatus and a method for improving nonlinearity of a power amplifier in a wireless communication system are provided. A transmission apparatus in a wireless communication system comprises: at least one processor; a transceiver; and an amplifier for amplifying a signal provided from the transceiver, wherein if a power of a signal inputted into the transceiver is smaller than a reference value, the transceiver attenuates the power of the signal based on a gain compensation value corresponding to the power of the signal.