Coffee is a popular beverage with many people at home and in the tea-room. Caffeine is a major chemical compound of coffee. A little caffeine is a stimulant to the movement and spiritual nerve, but much caffeine influences sleep, nervousness, non-concentration, headache and giddiness depending upon each person. The writer expresses the result of the caffeine content in the coffee which is collected from the coffee- shops of Seoul. The contents are as follows : 1) Caffeine content of the coffee of the tea-room was researched dividing into the central Seoul city and the outskirts of Seoul. 2) Caffeine content of the coffee in the outskirts tea-rooms is $0.32{sim}1.23mg/ml$ and the average is 0.546mg/ml (SD 0.19). 3) Caffeine content of the coffee of the central city is $0.34{sim}0.73mg/ml$ and the average is 0.513mg/ml(SD 0.12). 4) There was no difference between the outskirts and the central city. 5) Caffeine content of the coffee of the tea-rooms according to each season is going to be researched.