A medium transport device includes a transporting member, a medium offsetting member, a guide member, and an interlocking member. The guide member is located upstream of the transporting member in a medium transport direction. The guide member is movable between a first position, in which the guide member guides the medium toward the medium accommodating member, and a second position, in which the guide member guides the medium to a destination different from the medium accommodating member, to guide the medium. The interlocking member moves the guide member between the first position and the second position in conjunction with a movement of the medium offsetting member in a width direction of the medium offsetting member.