This study purports to evaluate the effects of the timeless son practice on high-school girl students’ concentration and emotional stability. In order to empirically test the hypotheses, I designed an experiment for the first grade students in a girls’ senior high school students, Seoul. The subjects were allocated to one of experimental group and control group with matching respectively(each group 17, total 34). While 12 times of the timeless son practice were conducted for four weeks to the experimental group, no experimental treatment was applied to the control group. The measurements of emotional stability and concentration were conducted before and after the experimental treatment and they were compared before & after test and experimental group & control group. For qualitative documentation, the mind-diary and description of impression for the practices were collected. The research findings are as follows: First, compared with the control group, the timeless son practice significantly contributed to decreasing the sense of inferiority in the experimental group. Second, compared with the control group, the timeless son practice significantly contributed to promotion of concentration in experimental group. I also collected and reviewed the mind practice diary written by the subjects for the qualitative documents. The documentation showed that the increased number of the mind practice deepened understanding of the application of the mind practice to everyday lives. Some additional effects of the timeless son practice are as follows: improvement in reading and controling one’s emotional state, positive mind in personal relationship, learning motivation, self-initiative in learning, peer group communication leading to self esteem, and improved problem solving skill. To summarize the empirical findings, the timeless son practice appeared to have positive effects on improvement of high school girl students’ emotional stability, sense of inferiority, & concentration.