The present invention relates to a packet transmission period control apparatus and method in a high-speed portable Internet network to provide a multimedia streaming service to a terminal. In the present invention, it sends a multimedia stream packet to the device in accordance with a first transmission cycle first. Then, after for receiving a response packet, the RR packet from the terminal check the reception state per packet, extracts the jitter (Jitter) value in the RR packet generating jitter list, the agent of the terminal that has already occurred on the basis of the generated jitter list 1 predicts a handoff occurrence time. Then, on the basis of the future occurs second after predicting the handoff occurrence time, the to be transmitted to the second handoff occurrence time and the second hand-off device during the elapsed time amount of packets on the basis of the predicted first handoff occurrence time It calculates a second transmission period. Claim a rate for transmitting packets at a faster rate than the second transmission interval is a first transmission period, and transmitting all of the packets to be transmitted to the terminal to the second hand-off the second terminal before the handoff starts with the packet to be transmitted before proceeding. Through this, also the reproduction of the stream must not be cut off during a second time at the handoff proceeds terminal. High-speed Portable Internet (HPi), hand-off, transmission period, the multimedia streaming service