The purpose of this study was to verify the effects of "quick grip exercise for 30 seconds", devised to improve junior high school students' grip strength. The subjects were 210 grade nine students (95 boys and 115 girls). They were divided into three groups ; the first group had the exercise 3 times a week with two "soft exercise balls", the second had the exercise 3 times a week without using balls, and the third had the exercise once a week with balls. The exercise was repeated during the warm-up time of the physical education class for three months from April to July in 2005. The main results of this study were as follows. 1) The grip strength of all three groups improved significantly. 2) The improvement degree of grip strength of girls in the first & second group was significantly higher than that of girls in the third group. 3) The ratio of the students who enjoyed the exercise with balls was significantly higher than that who exercised without using balls.