To provide a seedling transplanter having a simple machine structure, providing excellent ease of maintenance and preventing an untransplanted section of the seedling from being formed.

There is provided a seedling transplanter equipped with a seedling-transplanting part 4 for transplanting the seedlings on a plurality of rows, having a seedling-carrying platform 80 installed in the rear part of front wheels 6 and rear wheels 7, and having a seedling-carrying part 80b and partitioning wall parts 80a for partitioning the seedling-carrying part 80b by right and left each row, seedling-sending devices 97 for sending the seedlings on the seedling-carrying part 80b, seedling-transplanting devices 37 for transplanting the seedlings on a field, and seedling decrease-detecting devices 140 for detecting the decrease of the seedlings on the seedling-carrying part 80b, a buzzer 138, and a controller 157 operating the buzzer 138 when the decrease of the seedlings is detected by the seedling decrease-detecting devices 140. The seedling decrease-detecting devices 140 is constituted so as to detect the decrease of the seedlings in a plurality of the rows by one seedling decrease sensor 136. The formation of the untransplanted section can be prevented by the seedling decrease sensor 136, and the structure of the machine body becomes simpler to increase ease of maintenance compared to the case in which sensors are installed for every row.