The purpose of this study was to find out the factors of Knowledge and attitudes related to sun safety and to determine the factors affecting sun protection behavior. The subjects were 167 adults in their twenties living in Busan. The results were as follows. 1. Four factors of knowledge about sun safety were identified: ultraviolet ray risk, sunscreen, sun protective clothing, and nil protective color. 2. Four factors of attitudes toward sun exposure were identified: attractiveness, emotion, conformity, and health concern. 3. Four factors of sun protection behavior were identified: sunscreen/parasol, shade, hat/sunglasses, and sun protective clothing. 4. Compared to women, men were relatively more risk to skin damage due to less proportion that used sunscreen and a parasol. 5. Factors of sun protective behavior, such as sunscreen/parasol, shade, hat/sunglasses, and sun protective clothing, were associated with the Knowledge related to ultraviolet ray risk. 6. Wearing a hat and sunglasses was predicted by the attractiveness, which defined as positive attitudes toward tanned appearance. 7. Shade use was affected by the perception of sun exposure as happiness and relaxing. 8. Health concern was the strongest predictor of sunscreen/parasol use.