Reflectivity spectra of CaMnO 3 and LaMnO 3 were measured in a wide photon energy region between 5 meV and 30 eV at room temperature. Using the conductivity spectra obtained from the Kramers-Kronig analysis, electronic structures of the manganese oxides were investigated. In particular, the states near the Fermi energy E F, O 2p and Mn 3d (e g, t 2 g), were studied in detail. It was found that the O 2p band is located closer to E F than the Mn t 2 g band. For LaMnO 3, the filled Mn e g↑ 1 band is located closer to E F than any other valence band. The t 2 g-e g Hund exchange energy was found to be about 3.4 eV and the Jahn-Teller stabilization energy E 0 was estimated to be less than 0.5 eV.