The present invention relates to a method for retransmitting a packet in a mobile communication system. A waiting time for retransmission is established when a packet transmitted from a transmission unit to a receipt unit has no ACK message. A maximum number of times for retransmitting the packet is established when an NACK message is received. The ARQ transmitter moves to a discard state when the maximum management time of the ARQ block expires or the number of times of retransmissions exceeds the maximum number of times of retransmissions, and checks the ACK message receipt. The packet in the transmission buffer is discarded regardless of whether the distant message is transmitted or the discard message is transmitted or the discard message is checked when the ACK message is received.