The length of a delay time d from a suspension period starting point t1 until the application of a pulse voltage is begun is changed according to the length of the suspension period during which no data is collected at the time of m/z switching. It is thus ensured that the amount of product ions can be reliably restored at a suspension period termination point t2. In addition, the peak value of the pulse voltage is also changed according to the ionic strength immediately before entering the suspension period. The ion removal rate is thus increased when the amount of remaining ions is high, and the amount of remaining ions is reliably brought to zero within the same pulse width. As a result, crosstalk can be completely removed.