A method and apparatus for transmitting data in a wireless communication system is provided. A user equipment (UE) transmits the data in a first cell during a first random access procedure, i.e. early data transmission. The UE detects that transmission of the data in the first cell during the first random access procedure has failed, and prioritizes a second cell based on candidate cell information. After selecting the second cell, the UE transmits a failed part of the data in the second cell during a second random access procedure.