1. An image data management apparatus comprising: property information obtaining means for obtaining property information of an image data set to be managed; security processing method setting means for setting a security processing method for each of items of the property information; security processing means for carrying out security processing on each of the items of the property information according to the security processing method that has been set; attachment means for attaching the property information having been subjected to the security processing to the image data set; and image data storage means for storing the image data set attached with the property information.