IMAGE FORMING DEVICE

PROBLEM TO BE SOLVED: To provide an image forming device that surely detects the position of a toner image held by a sensor regardless of scratch or soil on an image carrier to be subjected to the detection and an error in the mounting of a regular reflection type photosensor. SOLUTION: A reference pattern image P for density detection and reference pattern images pP1 and pP2 for position detection, which are formed on a transfer carrying belt 60, are detected by the same reflection type photosensor 69. A threshold Vth used for the position detection is set on the basis of a base part output voltage Vsg obtained by the density detection and the minimum output voltage Vmin.