To provide an image forming device or a recording body conveying device capable of detecting a recording body with a corner fold in regards to a conveyed recording body.

A control part as a position detection processing means recognizes a position of a paper end part Pe as a width direction end part on a plurality of parts including a first detection part P1, which is one part of a corner fold region adjacent to a paper tip end Pt, that is a tip end in a conveying direction of the paper P as the recording body.