Packet transfer apparatus transmits/receives event sequence data such as audio data and music data over a fast serial network to which a plurality of devices are connected. The input section sequentially inputs event sequence data, which is sampled at a double rate by a sampling clock signal having a half period of the input clock signal. The input section can switch between a fast sampling mode where the event sequence data is sampled at a double rate by a sampling clock signal having a half period of the input clock signal and a regular sampling mode where the event sequence data is sampled at a regular rate by another sampling clock signal having the same period as the input clock signal, and further a regular packetizing section operates under the regular sampling mode for generating a packet of the inputted event sequence data in response to only one of the leading edge and the trailing edge of the input clock signal and adds the timestamp every time the predetermined number of data blocks are packetized by the regular packetizing section.