The first objective of this study was to investigate the relationship between positive and negative affect at three phases of a golf competition and performance in the competition. The second objective was to investigate the relationship between changes in positive and negative affect during the competition and performance in the competition. Thirty golfers who belonged to university golf clubs participated. The golfers answered the PANAS questionnaire immediately prior to the competition, immediately after the first half 9 holes, and immediately after the latter half 9 holes of the competition. Their performance in the competition was calculated by the mean score of the last 10 rounds of golf minus the score of the competition. Correlation coefficient showed that the performance in the first half 9 holes was significantly related to the positive affect immediately after the first 9 holes (r =.38), and the negative affect immediately after the first 9 holes (r =-.35). In addition, the correlation coefficient between the increased positive affect in the first 9 holes and the performance in the first half 9 holes (r =.46) and that between the increased negative affect in the first 9 holes and the performance in the first half 9 holes (r =-.38) was significant. These findings indicated that the positive and negative affect during a golf competition changed depending on the golfers' performance in the competition.