The present disclosure provides a method for transmitting a random access channel (RACH) by a UE in a wireless communication system. Particularly, the method includes receiving information about actually transmitted synchronization signal blocks (SBBs) and RACH configuration information about RACH resources and transmitting a RACH in at least one RACH resource among RACH resources mapped to actually transmitted SSBs on the basis of the information about actually transmitted SSBs and the RACH configuration information, wherein the actually transmitted SSBs are repeatedly mapped to RACH resources by a positive integer multiple of the number of the actually transmitted SSBs in a RACH configuration period based on the RACH configuration information.