This study was conducted to compare the perception and fast food usage patterns of adults classified by age in Busan. The survey was conducted from April 15 to June 15, 2017 by questionnaires and the data were analyzed using SPSS 24.0 Overall, 74.1%, 58.1%, 40.7%, 20.3%, 29.7% and 17.9% of individuals in their 20s, 30s, 40s, 50s, 60s and 70s, respectively, consumed fast foods more than once a week. Additionally, 66.0%, 52.5%, 25.7%, 16.0%, 22.9% and 11.7% of individuals in their 20s, 30s, 40s, 50s, 60s, and 70s, respectively, preferred fast foods. There was a significant difference in the basis for choosing menu among the groups, with 'preference' and 'price' being most important to those in their 20s and 30s, on the other hand 'preference' and 'companion' being most important to members of other age groups. As their age increased, individuals spent less money on fast food. Overall, 81.5%, 59.9%, 50.0%, 40.1%, 46.3%, and 28.4% of individuals in their 20s, 30s, 40s, 50s, 60s and 70s thought that fast food was a suitable substitute for a meal. Age affected the substitutability of fast food for a meal (P<0.001). Additionally, the ratio of individuals in their 20s and 30s that skipped breakfast was higher than in other age groups. In addition, age showed a significant positive correlation with obesity and dietary attitude, whereas it showed a negative correlation with nutrition knowledge, use frequency, perception degree and preference. Nutrition knowledge and dietary attitude showed no relationship with preference. These results imply that a nutrition education program should be developed and conducted to induce subjects to manage their dietary habit and develop healthier dietary patterns.