To facilitate the loading and unloading of a seedling box on a seedling box holding rack, effectively prevent the escape of the seedling box from the lateral holding plate of the inside receiving bar in the case of the loading and unloading work and the transportation of the rack holding the seedling box with a truck, and stably contact and hold the lower face of the seedling box while suppressing the lateral slippage of the box.

A number of rectangular seedling boxes are horizontally extended between an outer receiving bar of each stage positioned at the right or left and an inner receiving bar of each stage positioned at the center in a manner inclined to lift the box from the inner receiving bar side to the outer receiving bar side, and the seedling box is made to be freely insertable and removable for every stage in longitudinal direction or from outside. The inner receiving bar has a lateral holding plate receiving the lower face of the seedling box, having a blunt angle corrugated board shape extending outward in slantly rising manner and placed at the outer side of the lower end of the longitudinal receiving plate receiving the side face of the lowering inclined side of the seedling box. The receiving plate and the holding plate are continuously formed in longitudinal direction.