The purpose of this study is to develop a method to measure noninvasively the temperature distributions in tissues from the differences in sound speed before and after heating, using the characteristics that sound speed depends on the medium temperature. First, the phantom made of agar was placed in a water bath. We obtained the temperature distribution with the difference within 1℃ in phantom by subtracting the sound distribution before heating from that after heating. Then, we made the experiment with excised tissue in glucose solution. Tissue has to be placed in liquid which has the sound speed close to that in tissue in order to measure the small temperature difference. As a result, we measured the temperature difference below 1℃ in excised tissue.