A method and apparatus for handling data error in a data transmission system including a relay station which receives a data from a transmission apparatus and transmits the data to a receiving apparatus is provided. A relay station which transmits, to a receiving apparatus, a data received from a transmission apparatus, the relay station including: a data receiver to receive the data from the transmission apparatus; an error detector to detect whether an error of the received data is generated; and a data transmitter to transmit the received data and an error generation indicator for the received data to the receiving apparatus when the error is generated. According to the present invention, it is possible to combine transmitted data with retransmitted data and decode error-free data by transmitting data including a generated error to a receiving apparatus when error is again generated in the retransmitted data.