An image processing apparatus includes a sensor unit having a length in a main scanning direction greater than a length in a sub-scanning direction in which reading is performable by movement of the sensor unit. The image processing apparatus executes, twice, processing of moving the sensor unit from a reference position to a predetermined position and reading an image of a document to generate first image data and second image data, and outputs first extraction data generated by executing first extraction processing on the first image data, as one piece of page data, and to output second extraction data generated by executing second extraction processing on the second image data, as one piece of page data.