transmit the molecule ions of a specific mass to charge ratio from the selection unit 5 without transmitting the molecule ions having other mass to charge ratio the ac power source for collision rf 3 is connected to the linear multipolar electrodes third stage linear quadrupolar electrode a and b c and d are not illustrated of the collision chamber 9 and the ac voltage for collision high frequency voltage rf 3 can be applied to the linear multipolar electrodes a and b in addition the first dc power source dc 31 and the second dc power source dc 32 are connected to the linear multipolar electrodes third stage linear quadrupolar electrode a and b c and d are not illustrated and the first dc voltage dc 31 and the second dc voltage dc 32 can be applied to the linear multipolar electrodes a and b the control unit 14 can converge the target ions between the linear quadrupolar electrodes a and b c and d are not illustrated by carrying out control that applies the ac voltage for collision high frequency voltage rf 3 to the linear quadrupolar electrodes a and b c and d are not illustrated furthermore when the control unit 14 superimposes the first dc voltage dc 31 on the linear quadrupolar electrodes a and b c and d are not illustrated fragment ions can be generated by collision induced dissociation of the target ions according to the electrical potential difference or collision energy between the dc voltage for selection.