An image forming apparatus includes a plurality of image forming portions, a rotatable endless belt, a plurality of stretching rollers including an inner roller, an outer roller, a position changing mechanism, and a controller. During execution of a job for forming first toner images on a first recording material and second toner images on a second recording material subsequent to the first recording material, in a case that a changing operation for changing the position of the inner roller by the position changing mechanism after the first toner images are formed on the first recording material and before the second to toner images are transferred onto the second recording material is executed, a registration adjusting image is formed between the first toner images and the second toner images.