An image forming system comprising: an image forming apparatus comprising - a transfer means for transferring a toner image onto a printing material, and - a fixing roller means for fixing the transferred toner image on the printing material; and a cutting means for cutting the printing material onto which the toner image is fixed by the fixing roller means; characterised in that the image forming system further comprises: a determination means for determining: - a size of a first printing material on which an image has been fixed, - a finishing size of a second printing material, the finishing size being a size of the second printing material after it has been cut by the cutting means, and the second printing material being defined as printing material having an image fixed on it subsequent to the first printing material; and an adjustment means for executing an adjustment processing in the image forming system if the determination means determines that the finishing size of the second printing material is greater than the size of the first printing material, and for not executing the adjustment processing in the image forming system if the finishing size of the second printing material is not greater than the size of the first printing material, wherein the adjustment processing comprises making the temperature of the fixing roller means uniform between the centre and ends of the fixing roller means. an image forming apparatus comprising - a transfer means for transferring a toner image onto a printing material, and - a fixing roller means for fixing the transferred toner image on the printing material; and - a transfer means for transferring a toner image onto a printing material, and - a fixing roller means for fixing the transferred toner image on the printing material; and a cutting means for cutting the printing material onto which the toner image is fixed by the fixing roller means; a determination means for determining: - a size of a first printing material on which an image has been fixed, - a finishing size of a second printing material, the finishing size being a size of the second printing material after it has been cut by the cutting means, and the second printing material being defined as printing material having an image fixed on it subsequent to the first printing material; and - a size of a first printing material on which an image has been fixed, - a finishing size of a second printing material, the finishing size being a size of the second printing material after it has been cut by the cutting means, and the second printing material being defined as printing material having an image fixed on it subsequent to the first printing material; and an adjustment means for executing an adjustment processing in the image forming system if the determination means determines that the finishing size of the second printing material is greater than the size of the first printing material, and for not executing the adjustment processing in the image forming system if the finishing size of the second printing material is not greater than the size of the first printing material, wherein the adjustment processing comprises making the temperature of the fixing roller means uniform between the centre and ends of the fixing roller means.