A method of performing transmit power control is performed based on ISCP which a mobile terminal calculates from a downlink received signal. A transmission/reception unit of the mobile terminal transmits and receives a radio signal to/from a radio base station through an antenna. A transmission/reception control unit performs control relating to the signal processing in the transmission/reception unit. A control unit performs control concerning operation of each unit of the mobile terminal. A measurement unit measures ISCP and DPCH power from the signal received in the transceiver unit, and transmits the measured values to the control unit. A characteristic value conversion unit prepares a relation between the ISCP which satisfies a preset target BLER and the measured DPCH power, based on BLERs previously measured in a communication environment where the mobile terminal is located. A storage unit stores programs executed by the control unit and individual data such as a telephone directory. A display unit visually displays inputted/outputted information. An input unit includes key switches and others, and is used for a user to input information such as data and directions. An audio signal processing unit performs a conversion process between a modulation signal and an audio signal during a voice call.