The present invention provides an image forming apparatus including: a drive roller; an image forming unit; a fixing unit; a sub drive roller provided at the downstream side of the fixing unit, nipping and conveying a continuous-form-paper, on which the toner image is fixed, to the downstream side, a rotational speed of the sub drive roller being changable; a buffer unit provided between the fixing unit and the sub drive roller, being able to increase or decrease a buffer amount of the continuous-form-paper according to expansion or contraction of the continuous-form-paper in the fixing unit; a detection section that detects the buffer amount of the buffer unit; and a control section that controls the rotational speed of the sub drive roller based on the detection result of the detection section such that the buffer amount of the buffer unit is kept substantially constant.