An image processing apparatus which reads an image of a document and prints the read image on a sheet includes a detecting unit, an obtaining unit, and a controller. The detecting unit detects a size of the document. The obtaining unit obtains a size of the sheet. The controller performs control such that, in a case where the size of the sheet obtained by the obtaining unit is not a predetermined size, an image in a reading region based on the size of the document detected by the detecting unit is read, and in a case where the size of the sheet obtained by the obtaining unit is the predetermined size, an image in a reading region based on the size of the sheet is read.