In a mobile communication system, even when cells formed by fixed radio base stations are separated from each other, the switching operation between the cells is easily carried out to conduct continuous communication. A first-end radio device mounted in a first-end section of a mobile unit and linked with one of fixed radio base stations or a last-end radio device mounted in a last-end section of a mobile unit and linked with one of fixed radio base stations is selected. A communication network is established between the first-end or last-end radio device thus selected and a plurality of mobile terminals in the mobile unit. This makes it possible to construct a communicable zone (a virtual cell) on the mobile unit and hence elongates the ranges of cells formed by the base stations.