PURPOSE: To improve purity by mixing a raw material of a perovskite type oxide with a glass raw material having a lower melting point than that of the aforementioned raw material at a specific ratio, melting the resultant mixture by heating, then depositing the mixture, further heating the deposited substance, melting the glass matrix and separating the objective oxide.

CONSTITUTION: One or more carbonates or oxides such as BaCO3 of Ba, Ca, Mg, Sr and Pb are mixed with one or more of TiO2, ZrO2 and SnO2 in equimolar amounts and 30-70wt.% resultant perovskite type oxide raw material is mixed with 70-30wt.% glass raw material such as Li2B4O7 having a lower melting point and specific gravity than those of the aforementioned perovskite type oxide. The obtained mixture is then heated to melt and vitrify the glass raw material. Thereby, the perovskite type oxide raw material is dispersed in the resultant glass matrix. The obtained mixture is subsequently kept near the softening temperature of the glass matrix to deposit the perovskite type oxide, which is then heated to a higher temperature than the softening temperature of the glass matrix to melt the glass, float and separate the glass matrix having a low specific gravity and afford the purified perovskite type oxide.