An image reader is provided, which includes a feeder feeding a document sheet, a first reading sensor, a first reference member, a moving mechanism moving the first reading sensor to a document reading position to read an image of the document sheet and a reference reading position to read an image of the first reference member, and a controller that controls the moving mechanism to move the first reading sensor to the reference reading position, controls the first reading sensor to read the image of the first reference member, and controls the moving mechanism to move the first reading sensor to the document reading position after the first reading sensor reads the image of the first reference member. The controller controls the feeder to start feeding the document sheet to the document reading position before the first reading sensor reaches the document reading position from the reference reading position.