In dual connectivity or inter-base station carrier aggregation, synchronization between base stations is achieved while preventing processing load from increasing in user equipment. A method of acquiring broadcast information when configuring or performing inter-base station carrier aggregation in a mobile communication system including a first base station, a second base station, and a mobile device connected to the first base station, includes the steps of, at the first base station, creating first broadcast information about the second base station, except for information as to synchronization between base stations and supplying the first broadcast information to the mobile device on a dedicated radio resource control signal; and at the mobile device, after receiving the dedicated radio resource control signal, receiving the information as to synchronization between base stations over a physical broadcast channel of a first cell of the second base station based upon the first broadcast information.