A handover controlling method for switching a radio base station to which a mobile station is connected from a connection source radio base station to a connection target radio base station, the method comprising the steps of: generating, at the connection source radio base station, a handover request signal including radio related information retained by the connection source radio base station, and transmitting, from the connection source radio base station to the connection target radio base station, the handover request signal; the method being characterized by the steps of: extracting, at the connection target radio base station, difference information representing a difference between the radio related information included in the received handover request signal and radio related information set by the connection target radio base station; generating, at the connection target radio base station, a handover request acknowledgment signal for notifying the extracted difference information of the radio related information, and transmitting, from the connection target radio base station to the connection source radio base station, the handover request acknowledgment signal; generating, at the connection source radio base station, a handover command signal for notifying the difference information of the radio related information based on the received handover request acknowledgment signal, and transmitting, from the connection source radio base station to the mobile station, the handover command signal; and updating, at the mobile station, radio related information retained in the mobile station, based on the difference information of the radio related information notified by the received handover command signal. generating, at the connection source radio base station, a handover request signal including radio related information retained by the connection source radio base station, and transmitting, from the connection source radio base station to the connection target radio base station, the handover request signal; the method being characterized by the steps of: extracting, at the connection target radio base station, difference information representing a difference between the radio related information included in the received handover request signal and radio related information set by the connection target radio base station; generating, at the connection target radio base station, a handover request acknowledgment signal for notifying the extracted difference information of the radio related information, and transmitting, from the connection target radio base station to the connection source radio base station, the handover request acknowledgment signal; generating, at the connection source radio base station, a handover command signal for notifying the difference information of the radio related information based on the received handover request acknowledgment signal, and transmitting, from the connection source radio base station to the mobile station, the handover command signal; and updating, at the mobile station, radio related information retained in the mobile station, based on the difference information of the radio related information notified by the received handover command signal. extracting, at the connection target radio base station, difference information representing a difference between the radio related information included in the received handover request signal and radio related information set by the connection target radio base station; generating, at the connection target radio base station, a handover request acknowledgment signal for notifying the extracted difference information of the radio related information, and transmitting, from the connection target radio base station to the connection source radio base station, the handover request acknowledgment signal; generating, at the connection source radio base station, a handover command signal for notifying the difference information of the radio related information based on the received handover request acknowledgment signal, and transmitting, from the connection source radio base station to the mobile station, the handover command signal; and updating, at the mobile station, radio related information retained in the mobile station, based on the difference information of the radio related information notified by the received handover command signal.