PURPOSE: To facilitate the assembly of an electron lens to enhance mass production, and firmly support and fix its electrode to allow a highly precise assembling by providing a notch part capable of passing an insulating bar heated and welded to the surface of a large diameter cylindrical electrode.

CONSTITUTION: A fifth grid electrode 5 and a fourth grid electrode 4 inserted thereto are positioned by an assembly jig so that the bead support 41 of the electrode 4 is positioned in the axial middle of four bead supports 53 in the notch part 52 of the electrode 5. The electrodes 4, 5 fixed by the assembly jig are pressed onto a heating base 80, whereby prescribed areas of the support 41 of the electrode 4 and the supports 53 of the electrode 5 are pressed and buried in a bead glass (insulating bar) 40 heated and fused on the base 80. Since the electrodes 4, 5 are firmly fixed by, for example, the heated and fused glass 40, their concentric property can be precisely ensured, and also since an electron lens can be made to have a large aperture, a beam spot with less deviation can be provided.