Provided is a power allocation method and apparatus for providing a packet data service in a mobile communication system is capable of reducing outage of a line service while simultaneously providing the line service and the packet service. It is checked whether or not packet data traffic to be transmitted to a specified mobile station is newly generated. If the packet data traffic is newly generated, it is checked whether or not there is the mobile station making use of the line service where a current call is in progress. If there is the mobile station making use of the line service where the current call is in progress, it is checked whether or not the packet data traffic is currently transmitted to any other mobile station. If the packet data traffic is not currently transmitted to the other mobile station, the power transmitted to the mobile station making use of a new packet data service is gradually increased by a preset increment for a preset predetermined time. Thereby, it is possible to innovatively reduce the outage of the mobile station making use of the line service while simultaneously providing the line service and the packet service as compared with the prior art.