To provide a cut grass amount detector for suppressing leakage of cut grass, even in a structure in which, a sensor plate for detecting a storage amount of cut grass oscillates.SOLUTION: A cut grass amount detector comprises: a sensor plate 62 fitted to a detection opening 61a formed on a grass collection vessel, and supported so as to oscillate freely around a shaft core X； an energization member for energizing the sensor plate 62 in a closing direction； and a detection part for detecting oscillation when the sensor plate 62 oscillates against to energization force of the energization member by weight of the cut grass stored in the grass collection vessel, and the sensor plate 62 has a regulation member 76 facing an inner surface side of the grass collection vessel on an opening edge of the detection opening 61a and regulating movement of the cut grass toward a direction of an oscillation end.SELECTED DRAWING: Figure 9【課題】刈草の収容量を検知するセンサ板が揺動する構成であっても刈草の漏れ出しを抑制する刈草量検出装置を構成する。【解決手段】集草容器に形成された検出開口６１ａに嵌め込まれ、軸芯Ｘを中心に揺動自在に支持されるセンサ板６２と、センサ板６２を閉じ方向に付勢する付勢部材と、集草容器に収容された刈草の重量により付勢部材の付勢力に抗してセンサ板６２が揺動した際の揺動を検知する検知部とを備えると共に、センサ板６２が、検出開口６１ａの開口縁のうち集草容器の内面側に対し、揺動端の方向に向かう刈草の移動を規制する規制部材７６を備えた。【選択図】図９
