A method of controlling a handover procedure of a user terminal from a source master base station to a target master base station, the user terminal being connected to the source master base station and a secondary base station in accordance with a dual connectivity scheme, includes: transmitting, by the source master base station, a handover request to the target master base station; and receiving, by the source master base station, information related to necessity to change the secondary base station from the target master base station.