A method and apparatus for random access procedure based on a channel access priority class in a wireless communication system is provided. A wireless device transmits a random access preamble including a random access preamble identifier (RAPID). A wireless device receives, from a network, a downlink message including the RAPID and a specific channel access priority class (CAPC) mapped to the RAPID. A wireless device performing LBT procedure based on the specific CAPC. A wireless device transmits, to a network, an uplink message based on the downlink message.