To operate a device for stacking raising seedling boxes after seeding treatment or washing treatment in the specified number of stages, suitably with a simple structure.

A raising seedling box stacking device is provided with lift mechanism 13 for pushing up a raising seedling box 1, conveyed into a specified position being placed on a conveying device 8, by the set quantity, locking claws 15 displaced backward to the outside from a rising seedling box moving path by the contact with the upper face of the pushed-up rising seedling box 1 and energized to protrude into the rising seedling box moving path in association with the passage of the rising seedling box 1 so as to enter under flange parts 1a formed projecting at the peripheral part of the rising seedling box 1, and a means for impeding the energizing restoration of the locking claws 15 into a rising seedling box locking attitude.