In order to ascertain the effects of fluctuations and range of daily temperatures on the growth of rice, a pot(1/5, 000 are) experiment was conducted in the phytotron, Crop Experiment Station, in 1972. Seven treatment combinations of day-temperatures 25 and $30^{circ}C$ with night-temperatures 10, 15, 20 and $25^{circ}C$ were applied in three 10 days periods, in to which the tillering stage was split after rooting of the paddy, namely, early, middle and late. The results may be summarized as follows: 1. The number of tillers were maximum with the treatments of day-temperature $30^{circ}C$ and night-temperatures 20 as well as $25^{circ}C$ in the early and middle periods, while the effects were small in the late period. 2. Multiplying plant height and number of panicles resulted in a high figure by combining a day-temperature of $30^{circ}C$ with night-temperatures 20 as well as $25^{circ}C$ in the early and middle periods, and no differences in the late period. 3. The treatment in the early period yielded a high RGR(g/g/day), of which the treatment combinations of day-temperature $30^{circ}C$ with night-temperatures 20 and $25^{circ}C$ gave the highest figure. 4. High straw weight in ripening stage was obtained with the temperature treatments in the early period rather than those in the late period. 5. Accordingly, it seems that the effect of temperature on the emergence of tillers is the highest at the early stage of tillering.