Mesoporous cobalt oxide (Co₃O₄) was studied for air electrode of Li-air rechargeable battery. In this study, mesoporous Co₃O₄ with an average pore radius of 3.09 nm and BET surface area of 99 m²/g was successfully prepared by using mesoporous SiO₂ for template. Prepared mesoporous Co₃O₄ was applied for air electrode of Li-air battery after mixing with Pd and it was found that the cell showed a reasonably large discharge capacity of 481 mAh/g_-cat. at 0.1 mA/cm² at the initial cycle. Energy efficiency for charge and discharge was estimated to be ca. 75%. Raman spectroscopy suggests that the main product during discharge was Li₂O₂ and formation of Li₂CO₃ was hardly observed.