A sheet feeder including a driving mechanism moving a stopper, an end of the stopper in a first position being closer to a pickup roller axis than a part of a roller surface of a pickup roller, the end of the stopper in a second position being farther from the pickup roller axis than the part of the roller surface, and a movable set guide having a first surface facing in a particular direction to become farther from the roller surface, the first surface being farther from the pickup roller axis than all the roller surface when the set guide is in a third position and contacts the stopper in the first position, the first surface being closer to the pickup roller axis than the part of the roller surface when the set guide is in a fourth position and separated away from the stopper in the second position.