Provided is a mobile wireless communication system that improves response immediacy in a wireless communication system using an SCPC communication system. For this purpose, a base station and/or a plurality of mobile stations is provided with a number-of-channels switching means that monitors the communication state to create determination information for determining the necessity of switching the number of channels, and that switches the ratio of the number of channels for downlink communications and that for uplink communications, in a case where a change in the number of channels is necessary on the basis of the determination information.