A mobile communication system includes a plurality of base station apparatuses and a mobile station apparatus. The mobile station apparatus measures at predetermined intervals of time the quality of a signal received from each base station apparatus and transmits signal reception quality information indicating the quality of the signal to a first base station apparatus that is currently connected via radio to the mobile station apparatus. After a predetermined period of time has elapsed from the time that the signal reception quality for the first base station apparatus dropped to or below a first handover threshold, if the quality of the signal received from a second base station apparatus becomes equal to or higher than a second handover threshold, the first base station apparatus executes a handover to switch the radio connection of the mobile station apparatus from the first base station apparatus to the second base station apparatus.