1. A misregistration amount detector in a tandem image forming apparatus having a conveying body configured to convey paper on which a color image is to be printed, the misregistration amount detector comprising: an image creating part configured to create, on the conveying body, a first pattern for detecting an amount of misregistration of an image position related to a first color relative to an image position related to a second color other than the first color and a second pattern for measuring a conveyance speed of the conveying body, the first pattern and the second pattern being side by side in a conveyance direction of the conveying body; and a reading part configured to read the first pattern and the second pattern created on the conveying body by the image creating part.