PURPOSE: To align angle easily and accurately by setting the image pick-up angle of camera such that the electron line from second monitor will make predetermined angle with the incident beam of first monitor from a light source.

CONSTITUTION: An angle zig 64 is fixed on an outer case holder 38 such that a slit hole 65 will be placed between a light source 41 and a camera 46 of first monitor 45 light beam 42 is irradiated from the light source 41 and the angle is adjusted through a screw 40 to maximize the width of monitor screen 47. Then the end face of angle zig 64 is picked up by camera 56 or 57 of second monitor 55 through a prism 61 and the camera 56, 57 is rotated such that the electrone line 59 will be aligned with the line formed by angle edge 66. Thereafter the angle zig 64 is removed and an outer casing 11 is fixed to align a slit of deflection electrode through the first monitor 45 while the pattern of mesh electrode set on a chuck zig 53 is aligned with said line 59 by camera 57 and switched to camera 56 to align the pattern of stripe filter with said line 59 through an adjusting screw 51.