Upon receiving, from UE (200), SCG Failure Information that indicates that a radio link failure has occurred in a secondary cell group, eNB (100A) transmits, to gNB (100B), Secondary Node Modification Request to instruct to release a resource of a split bearer of only a predetermined layer and the layers below thereof in the secondary cell group. Based on the received Secondary Node Modification Request, the gNB (100B) releases the resource of the split bearer below the predetermined layer in the secondary cell group. The eNB (100A) deletes setting itself of the secondary cell group when a bearer belonging to the secondary cell group other than the split bearer is not set.