Method of manufacturing a gas sensor element

A laminated solid electrolyte gas sensor including a sensor element having great strength in which deformation at the time of manufacturing does not affect accuracy of assembling the gas sensor is provided. The amount of flexure in the first section Inl, which is a section extending in the longitudinal direction of the long plate-like sensor element from the position 8/27 of a size of the sensor element apart from one end of the sensor element to the other end, is set to be greater than or equal to 1/1360 and less than or equal to 1/670 with respect to the size in the longitudinal direction of the sensor element. The amount of flexure is a sum of a distance from a regression line to an upper side maximum displacement point and a distance from the regression line to a lower side maximum displacement point when calculating the regression line representing the relation of the position X in the longitudinal direction of the sensor element and the displacement Y in a thickness direction from a plurality of data sets showing the relation of the position X and the displacement Y, and illustrating a plurality of data points representing the plurality of data sets and the regression line on a X-Y plane.