A measurement control method in a mobile communication system is provided. The mobile communication system includes a first base station and a second base station which perform communications with a user apparatus by using inter-base-station carrier aggregation. The measurement control method includes a measurement instruction step of determining, by the second base station, a parameter used for measurement configuration information for the user apparatus and transmitting measurement instruction information including the parameters to the first base station; and a measurement configuration information providing step of generating, by the first base station which has received the measurement instruction information, the measurement configuration information in which the parameter included in the measurement instruction information is set, and transmitting the measurement configuration information to the user apparatus.