The object of the present invention is to provide a transmission power control method which enables the resolution of problems in a first control method for keeping the received power of packet signals in upstream radio channels constant and a second control method for keeping the SIR constant. The present invention relates to the transmission power control method for controlling the transmission power control of packet signals transmitted from a mobile station 30 via an upstream radio channel. The method comprises a step of measuring the traffic volume of the packet signals and a step of switching between the first control method and the second control method.