A data transfer control device, which transfers a large capacity of data speedily and sequentially, has three buffers that are used as a WR (write) buffer, an intermediate buffer, and an RD (read) buffer. To send data sequentially, the data transfer control device switches-over the buffers in one of the following three ways (A), (B), and (C), using determination flags indicating whether the buffers store effective data (data not yet referenced). A buffer control device switches-over (A) the WR buffer and RD buffer if a WR buffer effective flag 33 is on and an intermediate buffer effective flag 34 and an RD buffer effective flag 35 are off, (B) the WR buffer and the intermediate buffer if the WR buffer effective flag 33 and the RD buffer effective flag 35 are on and the intermediate buffer effective flag 34 is off, and (C) the intermediate buffer and the RD buffer if the intermediate buffer effective flag 34 is on and the RD buffer effective flag 35 is off.