An image reading device includes: light receiving sensors configured to read an image of a document conveyed in a sub-scanning direction and be arranged with an interval in a main scanning direction; one pair of document conveying rollers configured to be provided in front and back of the light receiving sensors in a document conveying direction; a detection unit configured to detect an image overlap amount in an image overlap area and/or an image missing amount in an image missing area; an adjustment amount determination unit configured to determine an adjustment amount for adjusting a distance between the document and the light receiving sensors based on the image overlap amount and/or image missing amount detected; and a drive unit configured to adjust a distance between the document and the light receiving sensors by displacing one of the document conveying rollers and light receiving sensors according to the adjustment amount.