To provide an image forming device capable of generating a printed matter imparted with information capable of determining easily genuineness, without requiring special equipment, and a genuineness determination system applied with the image forming device.

This image forming device includes a genuineness determination information generating part 4 of generating genuineness determination information for determining whether a recording medium formed with an image is reasonable or not, and an image forming part 30 for forming the image on the recording medium. The image forming part 30 forms, on the recording medium, at least one or more of markers including the genuineness determination information generated by the genuineness determination information generating part 4. The marker is formed of at least any of a yellow coloring material and a light yellow coloring material.