Abstract: A FIFO memory device for use in data transfer between data processing apparatuses having different data bus widths, has an input circuit 11 with a data bus width of k bits, an output circuit 12 with a data bus width of N×k bits (where N>1) that outputs data within the FIFO memory device, a writing pointer 2 that points to a data writing address of the FIFO memory device, a reading pointer 4 that points to a data reading address of the FIFO memory device, and a valid/invalid indicating circuit 6 that indicates whether or not data output to the output circuit 12 is valid.