A method and apparatus for managing a buffer of a Radio Access Station (RAS) in a communication system are provided. An available buffer space determiner sets a threshold for each service class for scheduling packet input/output of the buffer according to priority of a service class, estimates and stores, upon receipt of a packet at the buffer, an available space size of the buffer after the packet reception, compares the estimated available space size of the buffer with a first threshold corresponding to a first service class indicative of a service class of the packet, and schedules packet input/output of the buffer according to the comparison result. A processor module schedules packet input/output of the buffer according to an output of the available buffer space determiner. The present invention can improve quality of services through service differentiation based on priorities of service classes and buffer management based on characteristics of the corresponding service traffics.