Drag coefficient of trees was investigated with wind tunnel experiment using real young trees. After the measurement of drag force in several wind speed conditions, the leaf area density were counted every 10cm cubic space by cutting whole leaves within them. Then drag coefficient of tree was calculated using this leaf density as a reference area. The results obtained were as follows. 1. Wind velocity distribution behind tree was mainly dependent on the total leaf area and local arrangement of leaves. 2. The drag coefficient of trees whose shape is largely deformed by wind force becomes smaller with increasing wind velocity. 3. The leaf area density could partly explain the variation of tree's drag coefficient, though these relations were not so clear for some kinds of trees which have extremely crowded foliage or considerably apart from each other on the contrary.
