In this paper, changes of the micro-climatic characteristics in paddy field with the growth of paddy rice are investigated. This study was carried out in the paddy field of Kantc-Tozan Agricultural Experiment Station at Konosu, Saitama prefecture. The measurement was carried out at three periods, that is, the incipiency of tillering (July 20-21), the most prosperous period of tillering (August 9-10) and the adult period (October 24-26) as shown in Tab. 1. The conditions of paddy rice at each stage are described in Tab. 1. The items, points and methods of investigation at each period are given in Tab. 2.The results form this experiment are as follows.(1) Some samples of typical vertical distribution of temperature in the day time and the night at each growing period of paddy rice are shown in Fig. 1. It was recognized that the vertical temperature distributions in the day time, which we commonly say, “the incoming radiation type”, at the incipiency and at the most prosperous period of tillering were of the same type, but that of the adult period showed different type as the irrigation water disappeared. On the outgoing radiation type, that is, the vertical temperature distribution in the night, peak of minimum air tempearture at the most luxuriant part of rice was found clearly, in comparison with the incoming radiation type.(2) From Tab. 1 and Fig. 1, it is clearly recognized that the height to the most luxuriant part of paddy rice from the water surface coincides with the height where the peak of the maximum air temperature in the day time occurred. But the height of the maximum air temperature at the adult stage was found far above in comparison with that at the most prosperous period of tillering, because the part near the spikes of rice become the most luxuriant part at the adult stage.(3) The thermal diffusibility (α2) and the daily-range decreasing index (P) in the earth at each growing period were calculated as shown in Tab. 3. At the incipiency of tillering and at the most prosperous period of tillering, the values of α2 has a tendency, such that the surface layer (0-5cm) shows lower value than underlying layer (5-10cm), but at the adult period it shows reverse tendency.(4) The diurnal range of temperature at each period and position are shown in Fig. 2. It was found that at the incipiency of tillering the irrigation water had stronger influence upon the microlimatic characteristics, in comparison with the most prosperous period of tillering, the most luxuriant layer of paddy rice had larger influence.(5) Calculated from the distribution of wind velocity at the most prosperous period of tillering in paddy field, α (=h/Z0) is found to be 0.35-0.39 in comparison with 0.44 by Inoue and Tani.