Disclosed is a Rambus DRAM capable of reducing power consumption and layout area by enabling data readwrite control signal of accessed memory bank only, in a top memory bank and a bottom memory bank. The focusing electrode includes at least a first division electrode and a second division electrode arranged with a gap for controlling a scanning speed of the electron beams in common. The first shaft portion is mounted in a first bearing portion provided in the housing, and the second shaft portion is slidably mounted in a second bearing portion provided in the housing.