A medium transporting device includes: a transporting path; a contacted member that is provided on the transporting path to be movable in a medium width direction orthogonal to a medium transporting direction; a line-up member on the transporting path that lines up a position of the medium by sending the medium transported on the transporting path to the contacted member to bring the end of the medium in the medium width direction into contact with the contacted member; a displacement amount calculation unit that sets on a downstream side of the line-up member in the medium transporting direction, and calculates a misregistration amount of the medium in the medium width direction; and a contacted position control unit that controls a position of the contacted member by moving the contacted member in a direction of reducing the misregistration amount.