It is familiar that stress concentration and triaxiality have great influence upon the transition temperature of notch sensitivity of mild steel. So I performed impact tests of various notched specimens, and studied the influence of the followings : i.e. (1) Notch radius, and Thickness of specimens, (2) Notch angle, and Notch depth, (3) Side notches, A 13mm. thickness rimmed steel was used for the tests. Using the theory of the notch sensitivity of mild steel stated in the 1st. report, I obtained curves of mean energy transition temperatures vs. stress concentration and triaxiality matching very well with the experimental results. And also I verified that there is a certain relation between the absorbed energy at 0°C and the temperature on the 2.6kg-m/cm² (15Ft-Lb energy of the standard specimen) absorbed energy level. Some detailed discussion about absorbed energy will be left to the next report (the 3rd. report).