An automatic analyzer is capable of agitating a sample and a reagent by using ultrasonic waves having stable sound pressure, regardless of a characteristic variation of a piezoelectric element. The automatic analyzer agitates a sample and a reagent by using ultrasonic waves generated by driving a piezoelectric element. An amplifier configured to drive the piezoelectric element includes a voltage detection unit that detects a voltage applied to the piezoelectric element, and a current detection unit that detects a current flowing through the piezoelectric element. A calculation unit is configured to calculate effective electrical power based on a detected voltage and a detected current and determine an adjustment signal using the calculated effective electrical power and a predetermined target electrical power. An impedance matching circuit is configured to adjust output electrical power of the amplifier by changing a reactance component based on the adjustment signal determined by the calculation unit.

The present invention provides an automatic chemical analysis apparatus and an electrical impedance spectrometry device which make it possible to detect the state of a stirring mechanism prior to performing a stirring operation. The automatic chemical analysis apparatus dispenses a reagent and a sample to be analyzed into a reactor vessel 107, and performs stirring by applying sonic waves to the reactor vessel 107. The automatic chemical analysis apparatus comprises: a piezoelectric element 201 that generates sonic waves; a plurality of split electrodes 211 that are provided to the surface of the piezoelectric element 201; a power amplifier 203 that causes the piezoelectric element 201 to generate sonic waves by applying a voltage to each of the split electrodes 211; and a host computer and impedance measuring circuit that measure the electrical impedance spectrum of each split electrode 211 by applying a voltage to each of the split electrodes 211.