PURPOSE: To bring the inlet and the outlet of a whole electromagnet system close to each other to shorten the distance between them significantly by making the all deflection angles of deflection electromagnets for debunching of a charged particle beam to be larger than 90° so as to detour substantially the trajectory of the said beam.

CONSTITUTION: The 1st.∼the 3rd. deflection electromagnets 4a∼4c for debunching of an electron beam E have deflection angles larger than 90° respectively, and the edges of the respective magnetic fields are made all parallel to each other to construct a non-chromatic aberration system. The deflection angle of the 2nd. deflection electromagnet 4b is made to be twice of that of the 1st. deflection electromagnet 4a, and the deflection angle of the 3rd. deflection electromagnet 4c is made equal to that of the 1st. electromagnet 4a, and the deflection direction of the deflection electromagnet 4b is made reverse to that of the electromagnets 4a and 4c. Thereby by detouring the trajectory of the electron beam E substantially the inlet and the outlet of the whole electromagnet system can be brought close each other to shorten the distance between them significantly, so that the miniaturization of the equipment can be made possible.