PURPOSE: To continuously transfer a data group, and simultaneously to shorten its transferring time by providing a temporary storage means to store temporarily a preset plural number of frame data among the data groups to be transferred from an information recording medium to a buffer memory.

CONSTITUTION: On the reception of a read-out command from an external device, a data processing part 16 reads out the frame data stored in a magnetic tape 3, and deformats it. At the time of transmitting this deformatted data group to a buffer controller 15, the frame data corresponding to the first two groups of this data group is copied to the temporary storage means 17. This copied relevant information is read by a control part 11, and is transmitted to the buffer controller 15. In the buffer controller 15, it is judged whether write-in processing is completed or not based on the received relevant information, and in the case that write-in is completed, the transfer of the data group to the external device is executed immediately.