In a filing system, a data processing apparatus is connected to a file server via a transmission path. Image data of a document is captured into the data processing apparatus. The captured image data is stored onto an image storage medium. A plurality of owner identifications are acquired when the image data is captured. The owner identifications are correlated with the image data stored on the image storage medium, and the stored image data is allowed to be accessed when any of the owner identifications correlated with the image data is verified. The image data is output in a readable manner by retrieving the stored image data of the image storage medium when the access to the image data is allowed.