A device for identifying types of sheet materials has a detecting unit for detecting information regarding moisture of a sheet material; external force applicator for applying an external force to the sheet material; information obtaining unit for obtaining information according to a force that is attenuated by the presence of the sheet material when the external force is applied to the sheet material by the external force applicator; and a judging unit for identifying the type of the sheet material based on the information obtained from the detecting unit and the information obtained from the information obtaining unit.