A pair of velocity modulation coils are placed with a horizontal plane including a tube axis interposed therebetween, and a pair of magnetic substances are placed with a vertical plane including a tube axis interposed therebetween. A straight line portion of the velocity modulation coil extending substantially in parallel to the tube axis is placed between the magnetic substance and the tube axis. An interval D between the magnetic substance and the straight line portion is 1 to 3 mm. Assuming that the tube axis is a Z-axis, a size of the velocity modulation coil in a tube axis direction is L, and a position of an end of the velocity modulation coil on a side opposite to a phosphor screen in the tube axis direction is Z=0, a center point of the pair of magnetic substances in the tube axis direction is present in a range of Z=0.2.times.L to 0.9.times.L. Consequently, the sensitivity of velocity modulation can be enhanced while suppressing an increase in a driving power with a simple configuration.