A medium supporting device including a support part configured to support a roll body on which a sheet shaped medium is wound, a shaft serving as a rotary axis of the roll body and secured with the support part, and a driver configured to rotate the roll body supported by the support part. The shaft is secured to the support part by using a metal plate having a flat surface provided with an insertion hole, the insertion hole being a hole into which the shaft is inserted. An outer circumference part of the metal plate is restricted from moving in a rotation direction of the roll body relative to an inner circumference part of the support part.