An X-ray fluorescence analyzer is provided with an X-ray tube that irradiates primary X-rays, a first power supply that supplies a filament current, a second power supply that applies a tube voltage, a first diode connected to a power line, a Zener diode connected to the ground terminal, and an operational amplifier having an inverting input terminal, and a non-inverting input terminal. The non-inverting input terminal is connected to the power line, and the output terminal is connected to the second terminal and the inverting input terminal.