A mobile communication method according to the present invention includes: the steps of: acquiring, at a mobile station UE connected in a cell #1 controlled by an E-UTRAN-system radio base station eNB, information on a cell #2 controlled by a UTRAN, radio base station NodeB in response to an instruction from the radio base station eNB; reporting, from the mobile station UE to the radio base station eNB, the acquired information on the cell #2; and notifying, from the radio base station eNB to a UTRAN-system radio network controller RNC which provides service to the cell #2, information on the cell #1.