It was experimentally investigated in effects of high temperature and loading condition on the mechanical properties of concrete. This study is aimed to study the effect of elevated temperatures on mechanical properties of concrete according to compressive strength under loading. Tests were conducted on ${O}100{ imes}200mm$ cylinder specimens, which were tested under both stressed and unstressed conditions by steady-state test. The specimens were under-loaded to 0, 20, 40 percent of their ultimate compressive strength at room temperature and subjected to temperatures ranging from 100 to $700^{circ}C$, and the residual compressive strength compared to that observed at $20^{circ}C$. As a result, effect of mechanical properties of concrete at elevated temperature was especially subjected to transient creep more than thermal strain under loading in case of over $500^{circ}C$.