An image reading device includes a slide member, a guide rail, an engagement mechanism, a link member, and a link mechanism. The slide member abuts on and separates from a bottom portion of the reading unit, and when abutting on the bottom portion, supports the bottom portion of the reading unit. The guide rail is provided on a scanner frame and supports the slide member. The engagement mechanism changes in attitude between an engagement attitude to make an engagement between the engagement mechanism and a drive belt of a reading unit, and a release attitude to release the engagement. The link member links the slide member with the engagement member. When the slide member approaches the reading unit, the link mechanism causes the engagement mechanism to be in the engagement attitude, and when the slide member separates, the link mechanism causes the engagement mechanism to be in the release attitude.