A prefocus lens section is formed by a screen electrode and an additional
electrode. A main lens section is formed by a focus electrode, an anode
electrode and an intermediate electrode that is disposed between the
focus electrode and the anode electrode. Each of the focus electrode and
the intermediate electrode has a cylindrical electrode on at least one of
opposed faces thereof. The intermediate electrode and the anode electrode
have cylindrical electrodes on opposed faces thereof. A voltage with a
level higher than a focus voltage and lower than an anode voltage is
applied to the additional electrode and the intermediate electrode.