An image forming apparatus includes a main body, a sheet conveyance apparatus, and a control unit. The main body includes an image forming unit to form an image on a sheet. The sheet conveyance apparatus and the main body are detachable from each other and the sheet conveyance apparatus may convey the sheet to the image forming unit. The sheet conveyance apparatus includes a sheet conveyance path through which the sheet passes and a detection unit. The detection unit includes light emitting and receiving units that transmit light across the sheet conveyance path therebetween. The detection unit detects a reference and an edge position of the conveyed sheet in a width direction of the sheet orthogonal to a sheet conveyance direction. The control unit determines a position of the sheet based on detections of the reference and the edge position of the conveyed sheet by the detection unit.