PURPOSE: To provide a process capable of boring an electron beam passing hole with excellent quality by a method wherein only the big hole is formed in advance by etching until the diameter of the opening part of the big hole reaches the prescribed size, then a layer resisting agent etching liquid is formed in coating the bottom of said big hole followed by etching to make the diameter of the opening part of the small hole in the prescribed size.

CONSTITUTION: Only a big hole 14 having the opening part diameter D4 is formed by the method of spraying etching fluid while screening the small hole formation part and a sensitive film 12 with a polyester film 15. Thereby, the depth of the big hole 14 is so made that the thickness t2 from the small hole formation part may be the desired value. Next, the polyester film 15 is removed and a layer 16 resisting against etching liquid is formed so as to cover a sensitive film 12 from inside of the big hole 14, being followed by baking treatment. Further, the small hole 13 having the opening part diameter D3 is formed from only the small hole formation part. According to said method, the layer resisting against etching fluid is formed from the big hole side so as to simplify the work and make it unlikely to generate a defect of the electron beam passing hole due to a pin-hole, foam etc.