PURPOSE: To transfer data at high speed higher than the cycle time of a memory with the DMA transfer device provided with a central processing unit, memory connected to the bus of this central processing unit, DMAC part and external device so as to transfer data at high speed between the memory and the external device.

CONSTITUTION: A memory 13 is provided with four memory parts 7-10, adder part 4 for adding a high-order address 1A on an address bus 1 so as to prepare the next address value in advance, and selector part 12 for simultaneously accessing the memory parts 7-10 at the time of DMA transfer, connecting the input/output to a data bus 2 and switching the input/output.