A piezoelectric resonator including a base part, a first support part fixed to the base part, a beam part fixed to the first support part, a weight part fixed to the beam part, a drive unit provided on the beam part, and an adjusting magnet movable on a main surface of the base part. Furthermore, the weight part is formed of a magnet or a magnetic body, and the beam part extends in a direction along the main surface of the base part. With this configuration, displacement of the resonance frequency generated due to variation in a manufacturing process can be adjusted easily. Even when the resonance frequency is displaced from desired resonance frequency due to variation in the manufacturing process of a power generating element, the displacement can be easily adjusted and maximum efficiency can be obtained.