This study aims to suggest the proper ease for slim-fit jackets according to the number of buttons from a one-button jacket to four-button jackets for men in their 30’s. The researchers carried out both an appearance evaluation and movement functionality evaluation. The results are as follows: When conducting the appearance evaluations, meaningful differences were found. The one-button jacket showed high scores for the 7.5 cm ease. The two-button jacket and the three-button jacket showed high scores for the 10.5 cm ease. The four-button jacket showed a high score for the 13.5 cm ease. Next, the results of the movement functionality evaluation showed the same trend; as the ease was increased from 7.5 cm to 13.5 cm, the scores increased. This is because if the garments offer more ease, this gives room for actions. Additionally, it showed that if there were fewer jacket buttons, then the results showed a high score. The researchers believe that if the number of jacket buttons is lower, then the area of the V-zone increases, so that there is more room for movement. The study suggests a proper chest ease of 7.5 cm for the one-button jacket, 10.5 cm for the two-button jacket and three-button jacket, and 13.5 cm for the four-button jacket, respectively.