Document reading device and method for controlling the same

A document reading device, comprising:

• a document conveyer that conveys a document along a document conveying path;
• a first reader that reads, in a first reading position in the document conveying path, a first surface of the conveyed document such that a read area is larger than the conveyed document;
• a second reader that reads, in a second reading position in the document conveying path, a second surface that is opposite to the first surface such that a read area is larger than the conveyed document;
• a region detector capable of executing a process of detecting a first document region that is a region of a document in the first document image data obtained by the reading on the first surface and a process of detecting a second document region that is a region of the document in the second document image data obtained by the reading on the second surface;
• and
• a cropping processor that crops a document portion on the first surface from the first document image data as first cropped image data and crops a document portion on the second surface from the second document image data as second cropped image data, based on one of the first and second document regions that is successfully detected.