Provided is a seedling transplanter that can, at any time, detect the amount that a seedling mat is being fed. A seedling transplanter that comprises: a seedling platform that comprises loading surfaces that are aligned in a machine body width direction in accordance with a number of rows and that has a seedling mat loaded thereon at an incline; a planting claw that claws and plants seedlings from a bottom end of the seedling mat; a horizontal feed mechanism that is moved back and forth in the machine body width direction of the seedling platform; and a vertical feed mechanism that downwardly feeds the seedling mat that is on the seedling platform. The seedling transplanter also comprises a rotary body that is provided so as to protrude above the loading surfaces from an underside of the loading surfaces and that rotates in conjunction with the vertical feeding of the seedling mat by the vertical feed mechanism. The amount that the seedling mat is being fed is detected on the basis of the rotational speed of
