A directly heated cathode for electron tube having a stable electron emission characteristic and a low cut-off voltage is provided. The cathode comprises a base metal of an alloy consisting essentially of 20-30% by weight of tungsten and a trace amount to 0.25% by weight of zirconium, the balance being nickel, binder dots of metallic nickel powders distributed on a flat part at the front side of the base metal, and a layer of thermoelectron emission oxides laid on the flat part at the front side of the base metal. The layer of thermoelectron emission oxides is in direct contact with the flat part through clearances among the binder dots of the metallic nickel powders.