A method for providing scalable service in a wireless communication system is disclosed. In this method, the transmitting side device performs initial transmission of base layer signals to a user equipment (UE) based on a HARQ (Hybrid Automatic Repeat Request) scheme, and performs transmission of enhancement layer signals to the UE after finishing the initial transmission of the base layer signals. The base layer signals and the enhancement layer signals are for one scalable service. The base layer signals can be independently used at the UE without the enhancement layer signals, while the enhancement layer signals cannot be used at the UE without the base layer signals. The transmitting side device further performs retransmission of the base layer signals determined to be retransmitted based on the HARQ scheme while performing the initial transmission of the enhancement layer signals.