There are disclosed a radio communication device and others capable of generating in a short time a secret key common to a base station and a mobile station in a radio communication system using the MIMO technique and starting the encrypted communication at an early stage. In this device, in ST545, when a channel coincidence judgment unit (105) and a channel coincidence judgment processing unit (205) respectively judge that the channel matrix generated by the base station completely coincides with the channel matrix generated by the mobile station or they do not coincide completely but they can coincide finally by error correction of the secret key or the like, according to the judgment result indicated in the channel coincidence judgment signal generated in ST540-2, ST545 is followed by ST550. On the other hand, when the channel matrix generated by the base station does not coincide completely with the channel matrix generated by the mobile station and they do not coincide finally even after error correction of the secret key, ST510 is again executed after ST545.