A color image forming apparatus for forming a color image onto a transfer material by superimposing a plurality of unicolor toner images. The apparatus makes it possible to produce a high quality image through a secondary transferring operation with a good secondary transferring efficiency. At a pre-secondary transfer charge eliminating section, an electric potential difference between a grid electrode disposed at an upstream side and an opposing electrode is set at such a value that is greater than that between a grid electrode disposed at a downstream side and an opposing electrode.