An oxide having a perovskite structure, for example, barium titanate, is provided in which the particle diameter is as small as about 0.03 to 0.2 .mu.m, the amount of OH groups in the crystal lattice is less than about 0.2% by weight, the c/a axial ratio is as large as about 1.0033 or more and sufficient ferroelectricity is exhibited. Barium titanate is produced with steps of mixing a BaCO.sub.3 powder and a TiO.sub.2 powder having a specific surface area of about 10 m.sup.2 /g or more and heat-treating the mixed powder. In the heat treatment, in the case in which a partial pressure of oxygen is decreased to about 2.times.10.sup.3 Pa or less and more than about 2.times.10.sup.2 Pa, the heat treatment is performed at a temperature within the range of about 700 to 1100.degree. C., and in the case in which a partial pressure of oxygen is decreased to about 2.times.10.sup.2 Pa or less, the heat treatment is performed at a temperature within the range of about 600 to 1100.degree. C.