PROBLEM TO BE SOLVED: To solve such a problem that when a multi-steering lever is elevation-operated for only a little, elevating a pretreatment part which is excessively descended by a reaping height release control, the pretreatment part automatically elevation-drives, since a trigger switch is operated for the reaping height release control, the pretreatment part is elevated exceedingly to the assumption of an operator.SOLUTION: While the reaping height release-controlling means (21C) is in action, the automatic elevation drive of the pretreating part (5) by the automatic elevation-controlling means (21A) is restrained so as not to be performed, even if the elevating operation of the elevation-operating lever (11) is input by a pretreatment operation-detecting means (22).COPYRIGHT: (C)2013,JPO&INPIT【課題】刈高さ解除制御で下降させ過ぎた前処理部を少しだけ上昇させるためにマルチステアリングレバーを上昇操作すると、刈高さ解除制御のためにトリガースイッチを操作していることで前処理部が自動上昇駆動してしまい、オペレータの想定を超えて前処理部が上昇するという課題があった。【解決手段】刈高さ解除制御手段(21C)の作動中は、前処理操作検出手段(22)による昇降操作レバー(11)上昇操作を入力しても、自動昇降制御手段(21A)による前処理部(5)の自動上昇駆動を行わないように牽制した。【選択図】図8