An image reading device has: a light source at which plural light-emitting elements are arrayed; a detection unit that detects light amounts of illumination light which are emitted from the light-emitting elements and are reflected by a reference plate; a derivation unit; and an adjustment unit. On the basis of detected light amounts, the derivation unit derives difference amounts between a reference value and average values of light amounts per predetermined first number of adjacent light-emitting elements. On the basis of the derived difference amounts, the adjustment unit adjusts light amounts per the first number of light-emitting elements such that the average values become the reference value.