For the metal substrate of a strain sensor, a Mo-containing two-phase stainless steel SUS329 is used. When an insulating layer, electrodes and a resistor are formed on the metal substrate by baking their materials, the alpha phase in the stainless steel of the metal substrate changes to a sigma phase through the baking heat, and, as a result, the range of strain applicable to the sensor within the elastic region of the substrate is broadened and the residual strain of the substrate is reduced. T...