A high voltage generator including a Cockcroft-Walton circuit structured to receive alternating-current power supplied from an alternating-current power source and apply a potential difference to a load includes: three or more circuit boards arranged at intervals in a thickness direction thereof; capacitors, each of which is shaped flat and mounted to a corresponding one of the circuit boards; and diodes, each of which is connected to corresponding ones of the circuit boards. Out of the three or more circuit boards, each circuit board other than two circuit boards disposed at both ends of the arrangement of the three or more circuit boards includes indentations. Each of the diodes is disposed in a corresponding one of the indentations.