To provide a barium titanate piezoelectric ceramic which has higher d33and d31values using a two-step resistance heating sintering method of high practicality, and to provide the manufacturing method and various kinds of piezoelectric oscillators or the like using the ceramic at a low cost.

The 50-200 nm barium titanate powder with the nature of a piezoelectric substance is solidified to have a given shape, and is fired by two-step sintering temperatures by electric resistance heating or the like. A sintered body is formed being controlled in the maximum particle size of 5 μm or less with 1-2 μm of an average particle diameter, and having 98% or more of the density of the theoretical density of 6.01 g/cm3of barium titanate. The sintered body is performed with the polarization treatment for about 30 minutes by 1 kv/mm voltage at an ambient temperature or 80°C. In the two-step sintering method, in the atmosphere or in an oxygen atmosphere, by electric resistance heating, the sintered body is heated to 1,230°C-1,340°C of the first sintering temperature, and thereafter is lowered to 1,150°C-1,200°C of the second sintering temperature, and is sintered maintaining the temperature for a given length of time.

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