Image forming apparatus

An image forming apparatus includes a sheet conveyance portion, a recording portion, a sheet detection portion, and a control portion. In a duplex printing including a first and a second process of printing on a first surface and a second surface of the sheet, in the first process, the control portion calculates a center position of the sheet based on an edge position of the sheet on one side in the width direction and size information of the sheet, prints a first image on the first surface such that the first image is centered on the center position calculated, and prints a reference marker on the first surface. In the second process, the control portion calculates a correction magnification ratio based on a difference between a reading position and the printing position of the referencemarker, and corrects a size and a printing position of a second image. 本发明的图像形成装置具备：输送部、记录部、片材检测部、控制部。控制部在进行包含在片材的第一面印刷第一图像的第一工序、和在片材的第二面印刷第二图像的第二工序的双面印刷的情况下，基于在第一工序中利用片材检测部检测的片材的宽度方向的一侧的边缘位置、和片材的尺寸信息而计算片材的中央位置，并将第一图像的中心与所计算的