An image forming apparatus with an image forming part and a fixing part for fixing images on a recording medium measures, downstream of the fixing part in a transport path, speckles on a recording medium, and generates measured speckle data representing the measured speckles; stores measured speckle data with standard speckle data representing speckles on a recording medium that has not undergone a fixing process; further measures, upstream of the image forming part, measures speckles on a recording medium; and when the stored standard speckle data is the most analogous to speckles measured for the second time, applies corrections in order to compensate for the lengthening of the recording medium by a fixing process to document images formed thereon, and when the stored measured speckle data is the most analogous to speckles measured for the second time, does not perform the corrections in order to compensate for the lengthening.