An acceleration voltage generator is configured to cause a power MOSFET to turn on or off to switch a high direct-current voltage, so as to generate a high-voltage pulse for an ejection of ions from an ion ejector. A drive signal is used to cause the power MOSFET to turn on, and further includes a secondary drive signal to recharge a gate capacitance to cause the power MOSFET to stay in an on-state. In a drive signal generator, edge detection circuits generate an edge detection signal based on a start signal; selection circuits generate a primary drive signal by adjusting the edge detection signal in its signal width; and a secondary drive signal generator includes multiple circuit elements such as a semiconductor element, and generates the secondary drive signal.