PURPOSE: To improve the sensibility and resolution, by providing an ion accelerator and a plurality of energy analyzing means where the analyzing means is constructed with an outer cylindrical electrode and an inner cylindrical electrode while providing an electrode for passing ion through an ion incident hole during predetermined time width.

CONSTITUTION: An ion accelerating step A and an energy analyzing steps B1W B5 are constructed with an inner cylindrical electrode 1 and an outer cylindrical electrode 2 arranged coaxially. The electrode 1 is provided with a circular inlet slit 3 and a circular outlet slit 4 while an incident hole 6 provided with a timing electrode 5 is provided at the inlet end C1 of the initial analyzing step B1 and an outlet hole 7 is made at the exit end D5 of the final analyzing step B5. The accelerating step (A) is coupled through an ion inlet hole 10 to an ion generating source 9 connected with the exhaust system 8. An ion detector 11 is arranged at the rear of said hole 7 and coupled with the exhaust system 12. The detector 11 connected with the power source is connected through an amplifier 14 with an oscillograph. A timing pulse generator 16 is connected with the electrode 5 and the oscillograph 15, to analyze with high sensibility and resolution.