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.