Mitochondria in Pleurotus ostreatus was purified by stepped sucrose density gradient centrifugation. The activity of mitochondrial ATPase has been investigated during various times of illumination at each wavelength in the range of 400 nm to 700 nm. The mitochondrial ATPase activity was simulated 1,7 fold by 580 nm illumination compared with the broad wavelength group. The mitochondrial ATPase activity according to various times of illumination was stimulated 2.2 fold for 10 seconds at 580 nm compared with the broad wavelength group. The optimum pH and temperature of the mitochondrial ATPase were 7.4 and $60^{circ}C$, respectively. The activity of this enzyme was stimulated by 5 mmol $Fe^{3+}$, 5 mmol $Mg^{2+}$, 0.1 mmol $Ca^{2+}$ and 5 mmol $Fe^{2+}$ ion, but inhibited by 5 mmol $Na^{+}$ ion.