To accelerate discharging of ions, even in a pole trap of a simplified structure, and increase the ion amount storable, when using a long cylindrical ring electrode regarding a three-dimensional pole trap device and an ion detecting device, using the three-dimensional pole trapping device.

This device is constituted, by including a ring electrode 13 of which the substantially cylindrical interior is hollow; an end cap inlet electrode 14 which is installed at one end of the ring electrode 13 and receives the ions from an ion source, at least four pieces of rod-like electrodes 16 arranged in the hollow of the ring electrode 13; and an end cap exit electrode 15, which is installed at the other end side of the ring electrode 13 and receives the ions transported from the ring electrode 13.