An oxygen sensor consisting of a metal electrode formed on the surface of the side to be measured of a solid electrolyte sintering and of a reference oxygen pole formed by a mixture of metal and metal oxide on the opposite side of said surface of the side to be measured of the solid electrolyte sintering body, characterized in that, at least over the whole surface adjoining the mixture of metal and metal oxide on the side of the reference oxygen pole of the solid electrolyte sintering, a porous metal electrode is formed to insulate the solid electrolyte sintering from the mixture of metal and metal oxide, thereby improving the low temperature performance and internal impedance characteristics, as well as prolonging the life thereof. A method for manufacturing this sensor is also provided.