An image processing apparatus includes a memory, and a processor in communication with the memory, the processor configured to control a storage unit configured to associate and store a document and a thumbnail image of a top page of the document, a deletion unit configured to delete a page designated from among pages of the document stored in the storage unit, and a generation unit configured to, in a case where a page to be deleted by the deletion unit is a top page of the document, generate a thumbnail image based on the top page of the document after deletion.