In the mobile communication system, a total reception quality between a terminal and a base station is converged into a target quality, thereby suppressing a period in which the transmission power of a distant station becomes excessive.In a mobile communication terminal, when a target SIR for the transmission power control in a down link from a radio base station is controlled, when a transmission power control system using a moving average is adopted, an error occurrence situation is detected by a reception quality calculating unit, and when many errors occur in the short time in the shadow of a building and the like, the number of errors is replaced with a predetermined upper limit value, and the reception quality of the moving average is calculated by an up/down adjusting unit, and when this calculating result is better than a target reception quality, the going down timing and down width of the target SIR are changed, and the target SIR at that time is decided and controlled by a target SIR deciding unit. In this way, the period in which the transmission power of the radio station becomes excessive can be suppressed.