In a closed-loop TPC for a channel using a wireless resource, to which frequency hopping is applied, a high quality reception is achieved for all RBs without applying another technique to each RB. This transmission power control method, in a mobile communications system that transmits signals by frequency hopping in a plurality of resource blocks, includes a transmission power control method that transmission-power controls a channel in a closed loop using a wireless resource to which frequency hopping is applied, measures a reception channel quality of received signals for each resource block (RB1 and RB2), and transmits a TPC command-bit via a downlink so that the reception quality that is independently measured at each resource block among the resource blocks is made equal to a target reception quality.