A sidelink relay related operating method of a relay user equipment (UE) in a wireless communication system includes receiving a first message including a first cause value from a remote UE by the relay UE, configuring a second cause value based on the first cause value by the relay UE, and attempting RRC connection to a base station (BS) by transmitting a second message including the second cause value by the relay UE, and in this case, the first message is related to trigger of attempting RRC connection, and whether configuration of the second cause value of the relay UE is dependent upon the first cause value is determined based on a type of the first cause value.