Provided is a method and device for selectively transmitting a secondary cell group (SCG) failure information message to one of a master node (MN) and a secondary node (SN) in a wireless communication system. A user equipment (UE) detects a failure related to an SCG, and selectively transmits an SCG failure information message to one of an MN and an SN according to a reason for the failure related to the SCG. For example, if the reason for the failure related to the SCG is associated with the size of a hybrid automatic repeat request (HARQ) buffer, the UE ma transmit the SCG failure information message to the SN.