In an in-line type electron gun assembly wherein the grid electrodes of respective electron guns having the same function and constituting a main lens are formed into an integral grid structure, the grid structure is made up of two electrode members which are bonded together. The two electrode members are respectively provided with aligned three openings at corresponding positions. These openings are provided with long and short sleeves alternately such that the sum of the lengths of the long and short sleeves of the opposing openings of the first and second electrode members is equal to a predetermined length.