A scheduling method includes classifying, by a Point Coordinator (PC), terminals into delay-sensitive terminals and delay-insensitive terminals according to their traffic types; setting an initial value and a maximum value of a poll failure counter of each of the delay-sensitive terminals; polling each of the delay-sensitive terminals; determining whether there exists a delay-sensitive terminal of which a current value of the poll failure counter is less than the maximum value; and if there exists no delay-sensitive terminal of which the present value of the poll failure counter is less than the maximum value, sequentially polling the delay-sensitive terminals and the delay-insensitive terminals. Accordingly, QoS of voice packet transmission in an IP network can be guaranteed by granting priority to terminals generating traffic in reality according to traffic patterns of the terminals requiring strict QoS, such as a voice call service, and polling the terminals in a round robin mechanism.