A wiring substrate includes plural wiring layers and plural insulation layers being alternately stacked one on top of the other. The plural insulation layers are formed with insulation resin having the same composition. The plural insulation layers are formed with a filler having the same composition. The filler content of each of the plural insulation layers ranges from 30 vol % or more to 65 vol % or less. The thermal expansion coefficient of each of the plural insulation layers ranges from 12 ppm/° C. or more to 35 ppm/° C. or less.