A sheet holding structure comprises a container for holding fanfold paper layered by being alternately folded every predetermined length as a sheet. The container has upper and lower sections that are fixed to each other so as to be non-movable relative one another and that collectively form an accommodation portion that accommodates the fanfold paper. The lower section of the container has an inner wall surface formed in a concave shape along a lengthwise direction of the fanfold paper so that the fanfold paper curves in an inward direction and exerts an expanding force acting, at least in part, against the self-weight of the fanfold paper and in a direction opposite to the inward direction.