Provided is an image reading device including a platen that supports an original document on which an image is recorded, a reading unit that is opposed to the original document with the platen interposed therebetween, and includes a reading member which reads the image on the original document extending in a first direction, and a supporting member that supports the reading member, is movable along a second direction intersecting with the first direction, and is movably supported such that the reading member reads the image on the original document in the first and second directions, a guiding member that extends in the second direction and guides the supporting member when the supporting member is moved in the second direction, and a moving member that is disposed to be separated from the guiding member in the first direction and moves the supporting member along the second direction.