Power supply and mass spectrometer

The objective is to more rapidly switch the polarity of a high voltage and output the high voltage. Therefore, in the present invention a first switch circuit of a power supply has: a first switch element that is connected to an output terminal and to the control terminal of which a first drive signal is input; a plurality of second switch elements cascode-connected between the first switch element and a voltage source of a first polarity; and a first voltage-dividing circuit that divides the voltage between the voltage source of the first polarity and the output terminal and inputs a divided voltage to a control terminal of each of the plurality of second switch elements. In addition, a second switch circuit has: a third switch element that is connected to a voltage source of a second polarity and to the control terminal of which a second drive signal is input; a plurality of fourth switch elements cascode-connected between the third switch element and the output terminal; and a second voltage-dividing circuit that divides the voltage between the voltage source of the second polarity and the output terminal and inputs a divided voltage to a control terminal of each of the plurality of fourth switch elements.