A piezoelectric device includes a first piezoelectric substrate, a second piezoelectric substrate and an adhesive layer. First conductor patterns are provided on a front surface of the first piezoelectric substrate. A first piezoelectric element is defined by the first conductor patterns. Second conductor patterns are provided on a front surface of the second piezoelectric substrate. A second piezoelectric element is provided of these patterns. The adhesive layer adheres a rear surface of the first piezoelectric substrate and a rear surface of the second piezoelectric substrate to each other. The adhesive layer adheres the first and second substrates to each other such that a compressive stress is applied to the first and second piezoelectric substrates in a bonded state.