A control device and a control method and a mobile communication system

Controller (100) includes a first base station (200) constituting the first wireless zone, overlapping the first wireless zone within and relative transmission power than the first radio section is a lower second wireless interval It controls the operation of the second base station (300) to. Control device to the connection destination change request from the mobile terminal (400), connecting change determination unit determines whether the connection (114), for all the mobile terminals located in the first wireless zone, a first base station or measuring unit that measures the communication status from the second base station (112), change value determination unit that determines a change value of the transmission power of the second base station (113), first on the basis of the change value 2 comprising predicting unit that predicts a communication status after the change of the transmission power of the base station (112), the power changing unit for changing the transmission power of the second base station based on the change value (113). Power changing unit (113), when the mobile terminal changes the connection destination, in accordance with the measurement result and the prediction result of the communication status, to change the transmission power of the second base station.