Mobile radio equipment and a transmission rate controlling method thereof for reducing the rate of transmission between the mobile radio equipment and a base station when the transmission rate is beyond the capability of the application function of the mobile radio equipment to thereby use the resources of the radio base station effectively. A radio transmitter/receiver receives data or radio signals via an antenna. A transmission system function CPU converts or customizes the data to a data format acceptable to an application function CPU. Subsequently, the transmission system function CPU inputs the data via a data input/output section into a data input/output section of the application function CPU. A decoder 16 is fed with the data input to the data input/output section. After that, the data is decoded by the decoder, and output from an input/output section according to the format of the decoded data.