An image data processing apparatus for processing and transferring image data from memory cards to external devices, said apparatus comprising: an editing machine comprising a holding part for holding said memory cards, said memory cards for storing digital image data; a plurality of connecting parts for connecting said external devices to the editing machine, the external devices for storing digital image data; and data processing means for selectively delivering the digital image data stored in said memory card, held by said holding part, to a predetermined one or ones of said external devices connected to said connecting parts by either compression or expansion, and for delivering the digital image data stored in a predetermined one or ones of said external devices connected to said connecting parts to said memory cards held by said holding part by either compression or expansion.