Provided is a technique to secure compositional or microstructural uniformity of a ceramic sintered body while increasing the area of the ceramic sintered boy, thus improving basic performance including non-linearity, maximum withstand energy and aging characteristics. A plurality of small varistor pieces 11 and insulating resin are kneaded and extruded for shaping, whereby a sheet-form varistor layer 13 can be formed where a plurality of small varistor pieces 11 are spaced from one another and are aligned on the same plane, and the adjacent small varistor pieces 11 are bonded via insulating resin.