An image processing apparatus in which the reusability of digital image data is improved is disclosed. The apparatus includes an image reading unit reading a draft and obtaining the digitized image data; an image writing unit printing image data on a transfer paper; a recording unit recording image data and attached information of the image data; an external I/F unit transmitting and receiving image data and attached information of the image data; a first and a second image data processing units processing the image data from the image reading unit and the recording unit, respectively; and a bus controlling unit connecting each of the units. The first and the second image data processing units match the characteristics of the image data to prescribed characteristics so that the matched image data can be usable for both the image writing unit and the external device.