Water is one of the most important substances for plants. Limited water supplies directly influence crop yield, which eventually leads to food scarcity to humans. In this present study, we quantify the dynamics of a fluttering leaf as a function of the days without water. The deformation and vibration of a plant leaf can be induced by dropping an object or tapping with a finger. Using multiple cameras, the 3D motion of a leaf can be measured. We found that the frequency of a leaf increases with water stress. In terms of natural frequency, it tends to increase when moisture stress is applied to leaves. These results suggest that the stiffness of leaves according to moisture stress is related, so it can be used as an indicator of the overall performance of plants. This would lead to a nondestructive way to measure water stress through leaf stiffness.