An image forming apparatus forms a toner image onto sheets at the first feeding interval on a photoconductor or intermediate transfer member and, if the temperature of a fixing unit falls outside a set temperature range, the sheet layout is changed to a feeding interval wider than the first feeding interval. Adjustment processing is performed based on the image forming condition so that the feeding interval is changed to a wider one in the feeding interval changing step during image formation and it is determined in the determination step to perform adjustment processing, toner patch images are formed in an area where no toner image is formed on the photoconductor or intermediate transfer member . The adjustment processing is performed based on reading toner patch images.