The oxygen sorptive and catalytic properties of Mn-based perovskite-type oxides were investigated and compared with those of Co-based oxides. La₁-_xSr_xMnO₃ could be classified in two groups according to both the profiles of TPD chromatograms of oxygen and the defect structure. The first group (x=0 and 0.2) showed a large desorption peak centered at ca. 700°C (high-temperature peak). It was proposed that in these systems cation vacancies associated with the formation of Mn⁴⁺ were incorporated into the crystal lattice to mitigate the static Jahn-Teller distortion of Mn³⁺ at low temperatures and that on heating the vacancies were eliminated while giving rise to the oxygen desorption. On the other hand, the second group (x=0.4-1.0) were almost stoichiometric and it showed a small and plateau-like oxygen desorption peak below 500°C (low-temperature peak). The catalytic activities of La₁-_xSr_xMnO₃ were found to increase with increasing x and to reach a maximum at x=0.8. This trend coincided with that of the amounts of oxygen desorbed in the region of low-temperature peak. It is inferred that La₁-_xSr_xCoO₃ catalyzes oxidation reactions by “intrafacial” mechanism, in which oxygen vacancies in the bulk play an important role, while La₁-_xSr_xMnO₃ does by “suprafacial” mechanism, in which surface oxygen plays dominant roles. In La₁-_xSr_xMn_1-yCo_yO₃, the amounts of desorbed oxygen increased monotonously with increasing y while the catalytic activity reached a maximum at a value of y.