Disclosed are a scanner and an image forming apparatus including the same. The scanner may include a scanner unit; a support unit configured to support the scanning unit; a first pinion rotatably disposed on the support unit and configured to move along a first rack of a first surface of a guide member; and a second pinion rotatably disposed on the support unit and configured to move along a second rack of a second surface of the guide member such that the direction of rotation of the second pinion is opposite to the direction of rotation of the first pinion, the second surface of the guide member being different from the first surface of the guide member.