A mobile communication system, a radio switching method, a mobile base station and a mobile terminal in which the mobile terminal does not perform handover to a fixed base station while moving in/on a moving body to avert an adverse affect of variation of received field intensity on communication. Fixed base stations that are connected to a public telephone network are disposed along a traveling direction of a train. The train which a user who possesses a mobile terminal gets on is provided with a mobile base station capable of being connected to the fixed base stations. The mobile base station detects the mobile terminal entering into the communication area covered by the mobile base station and the train starting moving to the next station. Triggered by the two kinds of detection, the mobile base station takes over processes of handover to the fixed base station from the mobile terminal. While moving, the mobile base station performs handover to a next base station one after another. When the train approaches the next station, the mobile terminal performs handover to the fixed base station that covers the communication area around the station of arrival in behalf of the mobile base station.