A method of generating a data block to be transmitted from a protocol layer to a receiving side in a wireless communication system, the protocol layer having a header compression function, comprises generating at least one of a control packet which includes control information and a compressed packet generated by header compression for an upper layer data block, and generating a first lower layer data block which includes type indication information and the control packet, if the control packet is generated, the type indication information indicating a type of control information included in the generated control packet.