Provided is a method of performing a random access procedure, the method including: selecting, from among a plurality of Synchronization Signal Blocks (SSBs), a first SSB that exceeds a threshold value of signal power; transmitting a contention-based random access preamble corresponding to the first SSB; receiving a first Random Access Response (RAR) corresponding to the contention-based random access preamble; obtaining a first Media Access Control Protocol Data Unit (MAC PDU) corresponding to a size of uplink (UL) resource allocation in the first RAR; transmitting a message3 (Msg3) including the first MAC PDU; determining, by transmitting the Msg3, whether contention is resolved; and when the contention is not resolved, performing a contention-free random access procedure.