There is provided a method of producing a gas sensor element capable of detecting a concentration of specific ions based on a limiting current passing between a first electrode and a second electrode according to a concentration difference of the specific ions. The method includes a temperature raising step, a current measuring step and a control step. In the temperature raising step, a heater is energized to raise temperature of a solid electrolyte. In the current measuring step, a voltage is applied across the first and second electrodes and to measure a limiting current. In the control step, a part of a diffusion resistance layer is removed from the gas sensor element by using an ultrashort pulsed laser to control a diffusion length that is a length of an introduction path to maintain the limiting current to be within a final standard range.