Background and objective This study was conducted to investigate the effect of a horticultural activity program using pressed flowers on the prefrontal electroencephalogram (EEG) activity of university students. Methods This study was conducted from August 5 to October 12, 2021 on 31 students of D University. The program required the subjects to wear an EEG device and make fans decorated with pressed flowers. The program was divided into three stages: ① preparation stage: looking at a wall coated in white paint (2 minutes), ② working stage: designing pressed flowers on a fan (5 minutes), and ③ appreciation stage: looking at and appreciating the fans they made, decorated in pressed flowers (3 minutes). Total relative values were analyzed by dividing the sections of prefrontal θ, α, β, and ϒ waves into preparation, work, and appreciation, excluding delta waves that increase during sleep. Results Theta waves, which reflect the state of meditation, significantly increased on both left (p = .007) and right (p = .002) in the appreciation stage. On the other hand, there was a significant difference in alpha waves in the work stage (left: p < .001, right: p < .001). In addition, it was confirmed that beta waves reflecting attention, arousal, and active mental state increased in the work stage and decreased in the appreciation stage (left: p = .048, right: p = .010). In the case of gamma wave, there was no significant change. By gender, there was a significant decrease in theta waves (left: p = .034) and a significant increase in alpha waves on the left among male students (left: p = .026). For female students, theta waves significantly decreased in the work stage on the right (right: p = .038), and alpha waves significantly increased in the work stage (left: p = .002, right: p = .007). Conclusion As described above, it was possible to investigate the effect of horticultural activities using pressed flowers in each of the activity stages such as preparation, work, and appreciation on changes in the prefrontal EEG of university students.