Purpose : The purpose of this study was to compare the differences in muscle activity of the rectus abdominis, internal oblique, and external oblique muscles according to abdominal muscle exercise methods such as plank exercise, side plank exercise, and crunch exercise. Methods : This study was conducted with 37 college students. All subjects participating in this study were randomly assigned to the plank exercise group, the side plank exercise group, and the crunch exercise group. The exercise corresponding to each group was performed for a total of 8 weeks. The muscle activity of the abdominal muscles was measured before the experiment, 4 weeks, and 8 weeks, and the rectus abdominis, internal oblique, and external oblique muscles were measured. Results : As a result of comparison according to the period in the change in muscle activity of the abdominal muscles after exercise, the amount of change in muscle activity in all three muscles showed a significant difference. As a result of the post-hoc analysis, the muscle activity value of the internal oblique muscle after 4 weeks in the plank exercise showed a significant difference from the value after 8 weeks. In the side plank exercise, the muscle activity values of the rectus abdominis and external oblique muscles before and after 4 weeks showed significant differences from those after 8 weeks. And in the crunch exercise, the muscle activity value of the rectus abdominis muscle before exercise showed a significant difference from the value after 8 weeks. Conclusion : Plank exercise increases the muscle activity of the rectus abdominis, side plank exercise increases the rectus abdominis and external oblique muscles, and crunch exercise increases the muscle activity of the rectus abdominis. Therefore, it is thought that the stability of the trunk can be improved more efficiently if all three exercises are performed.