An image forming apparatus, including a reference guide, an oblique conveyer roller, and a curve guide, is provided. The reference guide is arranged on one side in a widthwise direction with respect to a widthwise center in a sheet conveyer path and regulates a widthwise position of the sheet. The oblique conveyer roller applies a conveying force acting in a direction toward downstream along a conveying direction and toward the reference guide to the sheet. The curve guide is arranged upstream with respect to the oblique conveyer roller along the conveying direction and forms a curve. The curve guide includes an inner guide and an outer guide. The outer guide has a constant curvature throughout a width regardless of a widthwise position therein. The inner guide has a protrusive portion protruding toward the outer guide at a position on the other side in the widthwise direction with respect to the widthwise center.