A roll medium support device includes a shaft member including an insertion part having a rectangular shape in cross section and configured to be inserted through a center hole of a roll medium, a support member having a rectangular first insertion hole through which the insertion part is inserted so that the support member supports the roll medium from a width direction, a rotating member rotatably provided to the support member and having a rectangular second insertion hole through which the insertion part is inserted, a pair of interlocking members extending along long sides of the second insertion hole in the rotating member, and an urging member urging the interlocking members towards each other. A distance between the interlocking members is shorter than a distance between short-side surfaces of the insertion part and longer than a distance between long-side surfaces of the insertion part.