An empirical equation of state for supercritical fluids has been derived based on the power laws and the thermodynamic equation of state P = (partial derivative S/partial derivative V)(T)T - (partial derivative U/partial derivative V)(T). The equation of state derived in this work is given by P=P*(T)-a(k)(T)Xe--X-b(k)(T)[X+c(k)(T)](4)X where P*(T), a(k)(T), b(k)(T), and c(k)(T) are functions of temperature and suffix k means a state of fluid such as k = l for the liquid-like region V < V-c and k = g for the gas-like region V > V-c in the supercritical region T > T-c. The quantity X is defined by X = (V - V-c)/V where V-c is the critical volume and T-c is the critical temperature. The equation of state for five fluids, neon, hydrogen, deuterium, carbon monoxide, and helium is given by a modified form P=P*(T)-{a(k)(T)+b(k)(T)[X+c(k)(T)](4)}Xe--X. Comparisons between the PV isotherms for methane calculated by the Benedict-Webb-Rubin (B-W-R), the Beattie-Bridgeman (B-B) equations of state and the equation of state in this work have been done and it is found that the present equation of state gives a good agreement with the data in the same order of accuracy as the B-W-R and B-B equations of state.