An acceleration voltage generator generates a high-voltage pulse applied to a push-out electrode, by operating a switch section to turn on and off a high direct-current voltage generated by a high-voltage power supply. A drive pulse signal is supplied from a controller to the switch section through a primary-side drive section, transformer, and secondary-side drive section. A primary-voltage controller receives a measurement result of ambient temperature of the acceleration voltage generator from a temperature sensor, and controls a primary-side power supply to change a primary-side voltage according to the temperature, thereby adjusting the voltage applied between the two ends of a primary winding of the transformer. The adjustment made on the primary-side voltage changes a slope angle of rise of a gate voltage in the MOSFET, and enables a correction to a discrepancy in the timing of the rise/fall of the high-voltage pulse caused by change in ambient temperature.