An apparatus and method for power allocation in a mobile communication system are provided. A transmitting method includes allocating a certain fraction of total power to a common control channel; allocating available power corresponding to the remaining fraction of the total power to remaining control channels except for the common control channel among control channels transmitted in a current time slot by considering the remaining control channels; calculating a gain value of each control channel according to power allocated to each control channel; and regulating a gain of each control channel, which is to be transmitted to one or more Access Terminals (ATs), according to the calculated gain value. Therefore, reception throughput of each control channel can be improved.