Wireless communication apparatuses, header compression methods thereof, and header decompression method thereof are provided. The header compression method enables the transceiver to establish a tunnel for a user equipment, enables the processing unit to receive a first packet, enables the processing unit to generate a second packet comprising an outer header set and the first packet, enables the processing unit to replace the outer header set of the second packet with a replaced header, and enables the transceiver to transmit the second packet by the tunnel according to an identity recorded in the replaced header. The header decompression method decompresses the header compressed by the header compression method.