It is generally recognized that the new leaf blade of rice plant emerges from the top of the front leaf sheath with regular interval one after another. The author intended to find some rules in the leaf appearance among tillers of one plant or among plants cultivated under many different conditions. The emergence date of every leaf was calculated, observing the each plant every day. The results are summarized as follows. 1. The mean appearance interval of the two successive leaves of main stem is a little longer than that of tillers. The later the tillering, the shorter the interval in the case of tillers. The main stem which has shorter interval shoots one more leaf, and heads a little later than the one having longer interval. 2. The appearance interval at early growth stage is short and then becomes gradually longer as the plant grows up, but sometimes the interval suddenly becomes much longer when the circumstances become unfavorite, especially when the nutrients are exhausted or the roots are injured. 3. In general, the interval corresponds well with the growth rate of rice plant, whereas the weight of dry matter becomes low under very high soil temperature (35∼37°C) although the interval is shortened and one or two more leaves are produced. 4. Apparent varietal difference in the interval of leaf appearance can be seen, but the reason is not known yet.