An image copier according to the invention comprises a scanner for reading an image and a printer for forming an image on sheet, and the scanner includes a document table for positioning an original document from which an image is to be read; a document holding cover holding the original document on the original document table and having a light-emitting element for detecting the size of an original document which emits light when the size of the original document is detected, a light source for irradiating the original document with light when an image on the original document is read, a light-receiving element for image reading which receives reflected light from the original document, a controller for the light-emitting element for detecting the size of an original document which controls the light-emitting element for detecting the thickness of the original document, a specific region determination unit for identifying a specific region based on the numbers of pixels in a main scanning direction and a sub scanning direction of image data, and a background correction unit for performing a process of correcting the background of an image which has been read. In the image copier according to the invention, see-through copying of the bottom side can be suppressed by performing a background correction process after an image is read without blocking a sensor hole of a sensor for detecting the size of the original document from light.