Abstract: A piezoelectric transducer is formed by fixedly laying a second oscillating plate over a first oscillating plate to which a piezoelectric oscillating assembly having a piezoelectric oscillating element is adhered, so as to define an acoustically sealed space. And, as the first oscillating plate oscillates by being driven by the oscillation of the piezoelectric oscillating assembly, the second oscillating plate oscillates by being driven thereby by way of the sealed space. Due to the shifting of the resonance frequencies of the piezoelectric oscillating assembly and the first and the second oscillating plates, and also due to the restriction of the oscillation by the sealed space, a wide frequency property is obtained, making this piezoelectric transducer particularly suitable for use as a speaker or as a microphone.