Disclosed are a terminal of an OFDMA-TDMA wireless Internet system capable of reducing transmission delay time while securing QoS for uplink data and a packet transmission method. A MAC layer of the terminal is divided into a MAC software part and a MAC hardware part to control priorities of data packets at a high level and low level. The high level priority controller carries out various fine control operations according to a QoS policy and the low level priority controller performs mechanical control operations based on a predetermined simple fixed priority policy.