An image processing apparatus includes a controller configured to execute a process on a result of reading on a plurality of documents. The controller obtains document data of a plurality of pages generated by reading the plurality of pages, executes detection of a heading region corresponding to a headline of a document on the obtained document data of the individual pages, and makes a determination as to whether reading order of the documents is appropriate by estimating the anteroposterior relationship among the pages based on presence or absence of the heading region in the document data of the individual pages.