PROBLEM TO BE SOLVED: To provide an automatic farmland water supply device capable of surely closing a water supply channel even if pebbles, gravel or the like is sandwiched between a water stop valve and a bottom surface of a valve chamber. SOLUTION: An automatic farmland water supply device 10 arranged in the middle of a water supply channel for guiding agricultural water from an irrigation canal to a farmland is arranged so as to be movable in the vertical direction, closes the water supply channel at a fully closed position lowered, and is fully opened at an elevated position. A plate-shaped water stop valve 20 that opens the water supply channel, a valve body accommodating portion 30 that accommodates the water stop valve 20 at the fully open position, and a water stop valve 20 that is provided above the valve body accommodating portion 30. A control device accommodating portion 50 for accommodating a control device 52 for controlling the vertical position is provided, and the outer periphery of at least the lower portion of the water stop valve 20 in the height direction when viewed from the thickness direction is a closed cell. It is made of a sponge and is an elastic body outer peripheral portion 22 that can be elastically pressed against the bottom surface of the water supply channel when the water stop valve 20 is lowered. [Selection diagram] Fig. 2【課題】小石や砂利などが、止水弁と弁室底面との間に挟み込まれても、給水路を確実に全閉に近い状態にすることができる農地自動給水装置を提供する。【解決手段】用水路から農地へ農業用水を導く給水路の途中に配置された農地自動給水装置１０は、上下方向移動可能に配置され、下降した全閉位置で給水路を閉じ、上昇した全開位置で給水路を開く板状体の止水弁２０と、全開位置での止水弁２０を収容する弁体収容部３０と、弁体収容部３０の上方位置に設けられ、止水弁２０の上下方向位置を制御する制御装置５２を収容する制御装置収容部５０と、を有してなり、止水弁２０の、厚さ方向から見て少なくとも高さ方向下側部分の外周が、独立気泡スポンジからなり、止水弁２０の下降時に、給水路の底面に弾力的に圧接可能な弾性体外周部２２とされている。【選択図】図２
