Fifo buffer device

As a FIFO buffer device, without decreasing the data transfer rate, to achieve a rewind function. Input data, together with written into the write FIFO buffer (11), is packetized by the packetizing FIFO buffer (13), written to the backup memory (20) which is formed on the buffer memory area (21). Multiplexer (15) is in the first mode while selectively outputting the output of the write FIFO buffer (11), in the second mode selects the packet data read out from the buffer memory area (21). Until the read FIFO buffer (12) becomes full, the first mode is selected.