Provided are a method for performing, by a user equipment (UE), transmission via only a primary path in a wireless communication system, and an apparatus supporting the same. The method may include: configuring a split bearer, which has multiple L2 entities for both a master cell group (MCG) and a secondary cell group (SCG); when the UE transits from a first state to a second state, reconfiguring the primary path of the split bearer autonomously; and performing the transmission via only the primary path of the split bearer, wherein the primary path is related to an L2 entity for the MCG.