To provide a fabrication method of a heater for an electron tube having outstanding characteristics of insulation and heat radiation.

In the fabricating method of the heater for the electron tube, which is an embodiment of hydrophobic electrodeposition using a hydrophobic electrodeposition apparatus 40, for an electrodeposition step of an alumina insulating layer, the humidity in the environment that comes in contact with the electrodeposition solution is kept 50% or less, preferably 20% or less, by using a nitrogen gas supply means 44, and the alumina insulating layer is electrodeposited to a metal wire immersed in the electrodeposition solution. Thereby, the water content of the electrodeposition solution is able to be decreased, and the alumina insulating layer with a uniform thickness around the metal wire is able to be electrodeposited, so that (1) the withstanding voltage between the heater and the cathode of the electron tube is increased, (2) the image apparition time is shortened by reducing the weight of over all alumina insulating layer, (3) the difference of thermal expansion between the outside and the inside the heater, when the heater is in operation, is reduced, and the film strength of the alumina insulating layer is increased.