The present invention relates to a method and apparatus of determining arrival time of data packet when a digital broadcast data stream is recorded. According to the present invention, two program clock reference values are extracted from a transport packet sequence, an average packet interval time is obtained based on both the difference between the two program clock reference values and the number of packets between two packets from which the two program clock reference values are extracted, and an arrival time of each packet between the two packets is determined by t(0)+I*t_av, where t_av is the average packet interval time, t(0) is the program clock reference value of the preceding one among the both packets, and I is an index indicative of the order of packet between the both packets.