In order to reduce a possibility of damaging a seedling in the event of transplant of unit nursery beds when the seedlings are replanted from a seedling tray that supports unit nursery beds individually planted with seedlings germinated from seeds to a hydroponic panel capable of securing a longer seedling-to-seedling distance, a seedling transplanter (1) includes: a seedling tray (3) supported by a frame (2) and configured to support a nursery bed (7) having unit nursery beds (71) separable from each other and arranged in two directions on a plane; a hydroponic panel (4) supported by the frame (2) and provided with holes (41) for storing the unit nursery beds (71), the hydroponic panel (4) serving as a transplant destination of the unit nursery beds (71) on the seedling tray (3); and a holding member (5) supported by the frame (2) pivotally around a vertical axis and vertically movably to separate the unit nursery bed (71) from the nursery bed (7) by holding any one or a plurality of the unit nursery beds (71) on the seedling tray (3) arranged in the outermost side of the nursery bed (7) from a lateral face side of the unit nursery bed (71) in a width direction of the unit nursery bed (71), insert the unit nursery bed (71) into the hole (41) of the hydroponic panel (4), and release the unit nursery bed (71).