Abstract: A power generator using a piezoelectric element is provided which generates electric power at a high efficiency. It has been determined that the efficiency of power generation varies as a function of the ratio of an initial unloaded value of the power generator to a prescribed voltage of the input of an electric power system. A high power generation efficiency can be obtained when the voltage ratio is in the range of approximately two to twenty. In particular, when the voltage ratio is in the range of approximately four to six, a maximum power generation efficiency can be obtained. The invention provides a small-sized, high performance power generator which can be used in practice in portable electronic devices or the like.