The present invention relates to a gas sensor electrode including a conductive particle phase made of Pt or Pt alloy and a ceramic particle phase being mixed and dispersed, wherein a rate of content of the ceramic particle phase is 6.0 to 22.0 mass%, and a void ratio is 2.5 to 10.0%, and a dispersion degree of the conductive particle phase per length of 25 µm on the electrode surface is 0.60 to 0.85 µm, and a dispersion degree of the conductive particle phase in the electrode cross section per length of 100 µm in a direction parallel to the electrode surface is 2.0 to 4.0 µm. This electrode can be produced by firing a metal paste made by dispersing, in a solvent, a conductive particle having a core/shell structure in which a core particle such as Pt is covered with a ceramic shell and ceramic powder. The gas sensor electrode according to the present invention has a high electrode activity.