There is provided a data transmitting/receiving method in an HARQ data communication system. To transmit a physical layer information stream having a plurality of sub-blocks, each sub-block having an error correction code, a QoS (Quality of Service), and a priority if the sub-blocks has a different QoS, the encoded physical layer information stream is divided into a plurality of slots. The slot data are sequentially transmitted to a receiver in predetermined time intervals. If an HARQ (Hybrid Automatic Repeat Request) message for the initial slot data is received from the receiver, indicating that at least one of the sub-block in the initial slot data has a reception error and the other sub-blocks are good in reception, slot data with a sub-block having an error repeated within the number of the sub-blocks is retransmitted after transmission of initial slot data.