PROBLEM TO BE SOLVED: To improve workability of seedling replenishment in a riding-type rice transplanter in which a preliminary seedling stand is supported by a front-back support mechanism so as to be capable of changing its position in the front-rear direction. SOLUTION: A support for supporting a plurality of preliminary seedling placing stands 31, 32 in a first state in which they are vertically arranged at a predetermined interval and in a second state in which they are arranged in a row in the front-rear direction so that their positions can be changed. A mechanism 45, an operation tool for artificially operating the preliminary seedling placing stands 31, 32 in the first state and the second state, and the preliminary seedling placing stands 31, 32 can be held in the first state and the second state. And a holding mechanism. To artificially change the positions of the front and rear support mechanisms 37 for supporting the preliminary seedling stand 31, 32 and the support mechanism 45 so that the positions thereof can be changed in the front and rear direction, and the positions of the preliminary seedling stand 31, 32 and the support mechanism 45 in the front and rear direction. And the front-rear holding mechanism capable of holding the preliminary seedling stand 31, 32 and the support mechanism 45 at a desired position in the front-rear direction. [Selection diagram] Fig. 6【課題】予備苗のせ台が前後支持機構により前後方向に位置変更可能に支持された乗用型田植機において、苗の補給の作業性を高める。【解決手段】複数の予備苗のせ台３１，３２を上下方向に所定の間隔を置いて配置された第１状態及び前後方向に一列状に配置された第２状態に位置変更可能に支持する支持機構４５と、予備苗のせ台３１，３２を第１状態及び第２状態に人為的に操作する為の操作具と、予備苗のせ台３１，３２を第１状態及び第２状態に保持可能な保持機構とが備えられる。予備苗のせ台３１，３２及び支持機構４５を前後方向に位置変更可能に支持する前後支持機構３７と、予備苗のせ台３１，３２及び支持機構４５の位置を前後方向に人為的に変更する為の前後操作具と、予備苗のせ台３１，３２及び支持機構４５を前後方向の所望の位置に保持可能な前後保持機構とが備えられる。【選択図】図６
