PURPOSE: To perform data transfer in a short time without the intervention of a CPU by providing at least two buffer devices between a block type magnetic tape device and a sector type magnetic disk device.

CONSTITUTION: The magnetic tape device 1 and magnetic disk device 5 are connected mutually by data transfer paths 2 and 4 through a data transfer controller 3. The data transfer controller 3 consists of a magnetic tape buffer device BMF 7 and a magnetic disk buffer device BFD 8 which are controlled by a microprocessor MPU 6. For example, when data transfer mode from the tape device 1 to the disk device 5 is set under the control of the MPU 6, one-block data from the tape device 1 is stored in the memory in the BMF 7, and the BFD 8 is placed in data receiving mode to store the data in the memory. Then, the data from the BFD 8 is written in free sectors of the disk 5. Reverse transfer is the same. Thus, the data transfer time is shortened.