| 摘要 |
A first degradation degree detector detects a first degradation degree of one of a plurality of image forming devices for forming toner images, respectively, which is provided at an extreme downstream position in a direction of rotation of an intermediate transfer member. A first degradation degree judgment device judges whether or not the first degradation degree of the extreme downstream image forming device detected by the first degradation degree detector reaches a first level of deterioration. A bias controller decreases a bias to be applied by a transfer device to transfer the toner images, which are formed by the plurality of image forming devices and transferred on the intermediate transfer member, onto a transfer sheet, when the first degradation degree judgment device judges that the first degradation degree of the extreme downstream image forming device detected by the first degradation degree detector reaches the first level.
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