In a wireless communication system operating in a mixed channel environment involving A-DPCH (Associated--Dedicated Physical CHannel) to which soft handover applies and HS-DPCCH (High Speed--Dedicated Physical Control CHannel) to which hard handover applies, in order to keep the received SIR of HS-DPCCH at the required SIR by performing transmission power control for HS-DPCCH appropriately, HO judgment section 30 judges whether A-DPCH is in a soft handover state or not, transmission radio section 42 sets the transmission power of HS-DPCCH into a power equal to the transmission power of A-DPCH when A-DPCH is not in a soft handover state, whereas the transmission power of HS-DPCCH is set at an addition of the transmission power of A-DPCH and an offset when A-DPCH is in a soft handover state.