A medium correcting device includes: a first holding body that holds a first rotating body having a surface moving circumferentially; a second holding body that holds a second rotating body having a surface that moves following the circumferential movement of the first rotating body and becoming a coupled body incorporating the first and second rotating bodies; a rotation shaft connected to a driving system when the coupled body is housed in a housing body and separated from the driving system when the coupled body is removed; an off-center cam eccentrically fixed to the rotation shaft, presses one rotating body against the other by an amount of pressing according to an angle of the off-center cam, the amount being larger in a downward eccentric direction; and a center-of-gravity correction section fixed to the rotation shaft, causing a larger torque than a torque produced by the off-center cam's own gravity.