A mobile radio communication system of this invention includes a plurality of base stations connected to a network through wire lines, respectively, and a plurality of mobile stations respectively connected to the base stations through radio channels. A plurality of radio frequencies are shared by the base and mobile stations. At least one of transmission signals having these radio frequencies is arranged as a time frame constituted by a plurality of time-divisionally multiplexed time slots. At least either of the base and mobile stations includes a use state determining section for determining the use states of each of the radio frequencies and each of the time slots on the basis of a received wave, a radio channel determining section, and a radio channel establishing section, which are arranged as function programs of software. On the basis of a determination result provided by the use state determining section, a radio frequency and a time slot for connecting the base and mobile stations by radio are determined, and a radio channel based on the determined radio frequency and time slot is established between the base and mobile stations.