PROBLEM TO BE SOLVED: To lighten an operation load on seedling raising. SOLUTION: Nursery boxes are transferred to a pool P for seedling raising boxes without watering the seedling raising boxes (b) in a seeding process A. In a raising process B, after the seedling raising boxes are transferred to the pool P for seedling raising boxes, the pool P for seedling raising boxes is watered and water is drained to water the seedling raising boxes (b). Then seed rice is germinated and raised.