PURPOSE: To provide a pot seedling-planting device capable of being rotated at a high speed and smoothly.

CONSTITUTION: This seedling-planting device for a seedling transplanter is equipped with the first sun gear 7, the first epicyclic gear 8, the second epicyclic gear 9, the second sun gear 10, furthermore the third epicyclic gear 11 revolved round the first sun gear 7, the fourth epicyclic gear 12 incorporatively rotated on the same shaft with the third epicyclic gear 11, and the third sun gear 13 engaged with the fourth epicyclic gear 12 and rotated on the same shaft as that of the first sun gear 7. The first epicyclic gear 8 and the third epicyclic gear 11 are disposed so as to be rotated in the same direction as that of the first sun gear 7 and at a rotation rate of two times that of the first sun gear 7. Non-equal diameter gears are adopted only for a transmission system from the second epicyclic gear 9 to the second sun gear 10 and for a transmission system from the fourth epicyclic gear 12 to the third sun gear 13, and the transmission rotation ratios of the systems can be changed by changing the rotation angles of the gears. Two planting tines 16 attached to both the end sides of a rotary case 5 are rotated at the same angles as those of the second sun gear 10 and the third sun gear 13 through link mechanisms, respectively.