The aim of this research was to examine the thermal performance of the flat roof in proportion to various directional changes, the results of which were drawn from the miniature model experiment. In this process, various thermal environmental factors were measured and compared with one another to research their aspects of changes. The brief results of this research are as follows: 1) The indoor temperature and load per hour in proportion to directional changes shows the same degree of changes. As for the results of the clear-sky and cloudy-sky experiments, both of them generally appear advantageous in the order of S, $S-30^{cire}C$-E, $S-30^{cire}C$-W, $S-60^{cire}C$-W, E, $S-60^{cire}C$-E, despite slight differences in the indoor temperature and load per hour in proportion to directional changes. 2) As for the total load of degree day per direction of the clear-sky and cloudy-sky experiments, both of them shows their advantageous results in the order of S, $S-30^{cire}C$-E, $S-30^{cire}C$-W, $S-60^{cire}C$-W, E, $S-60^{cire}C$-E, despite minor differences in their loads. 3) As for the peak load of degree hour, while the clear-sky experiment shows its advantage in the order of $S-30^{cire}C$-E, S, $-30^{cire}C$-W, $S-60^{cire}C$-W, E, $S-60^{cire}C$-E, the cloudy-sky experiment does so in the order of S, $S-30^{cire}C$-E, $S-30^{cire}C$-W, E, $S-60^{cire}C$-W, $S-60^{cire}C$-E.