An agricultural greenhouse (1) for growing a crop (4), wherein a control device (2) controls the degree of opening of ventilation windows (30, 31) provided in the greenhouse in accordance with detection results pertaining to whether or not it is raining that are based on a detection value from a rain sensor (53). The control device is equipped with control units (20, 21). In cases in which the detection results based on the detection value from the rain sensor indicate it is raining, if a state is detected in which the amount of solar radiation detected by a solar radiation sensor (52) during a daylight time period is equal to or larger than a prescribed non-rain solar radiation value corresponding to the amount of solar radiation when it is not raining and this detected state continues for a prescribed non-rain determination time period or longer, the control units (20, 21) determine that the detection result of rain is a false detection and control the degree of opening of the ventilation windows to open wider than the set opening degree for periods of rain.
