An image reading apparatus that includes an image reading portion, a tray, a first regulation member movable in a width direction on the tray, a second regulation member movable in association with the first regulation member, a first rotating portion and a second rotating portion that are each capable of being rotated by a sheet on the tray, and a sensor portion configured to generate a signal based on rotations of the first and second rotating portions. The first rotating portion is located between the first regulation member and the second regulation member that regulate both edges of a sheet having a minimum width, and the second rotating portion is located between the other edge of a sheet having a smaller width and the first regulation member, when sheets having different widths are supported on the tray with each having one edge aligned with the first regulation member.