A roll body supporting device that rotatably supports a roll body includes a shaft member inserted into a core of the roll body, a shaft outer circumference member fixed to an outer circumference of the shaft member, a core support member that is inwardly in contact with and fits on the core, and a rotation support section that connects the shaft outer circumference member to the core support member and supports the core support member in a manner to be rotatable about the shaft member relative to the shaft outer circumference member.