PURPOSE: To mount an electron gun correctly and simply on a pin fitting body by guiding an exhaust pipe into the exhaust pipe positioning hold of an exhaust pipe guide followed by guiding each pin terminal to the prescribed pin terminal positioning concave part of a pin terminal guide.

CONSTITUTION: When an exhaust pipe guide 18, a pin terminal guide 22 and the clipping body of an electron gun holder 31 are closed, the electron gun 34 goes down to guide its exhaust pipe 35 from the guiding part 21 of the exhaust pipe guide 18 to the exhaust pipe positioning hole 20 for positioning while said pipe 35 being inserted into an exhaust pipe insertion hole 36 of an electron gun holder 31 through a hole 23 of the pin terminal guide 22. Here, the exhaust pipe guide 18 is opened, further the electron gun 34 goes down to guide its each pin terminal 37 from each guiding part 25 of the pin terminal guide 22 to the prescribed pin terminal positioning concave part 24 for positioning, while inserting them into the prescribed pin terminal fitting holes 38 of the electron gun holder 31 for opening the pin terminal guide 22, then the electron gun 34 further goes down to completely fit its each pin terminal 37 into each pin terminal fitting hole 38 of the electron gun holder 31 for finishing the mounting of the electron gun 34.