A radio communication system includes a base station of a radio communication system A, a base station of a radio communication system B operation in non-synchronized way with the base station, and a mobile station capable of communicating with both of the radio communication system A and the radio communication system B. The base station includes a radio unit for transmitting/receiving a radio wave to/from the mobile station and a system information estimation unit for estimating the system information on the radio communication system B and outputting the system estimation information. The radio unit of the base station reports the system estimation information on the base station to the mobile station. The mobile station receives the system estimation information on the base station in advance so as to perform effective switching without using a cabled connection from the radio communication system A to the radio communication system B via a relay device or the like.