A wiring board includes an insulating resin layer including resin material and filler, and a conductive circuit layer laminated on a surface of the insulating resin layer and having wiring patterns. The filler has particle diameters of 15% or less of a minimum width of the wiring patterns when the particle diameters of the filler is measured in a unit range defined such that the unit range has a width and a length where the length is measured from the surface of the insulating resin layer and is selected from a smaller of twice the minimum width of the wiring patterns and a plate thickness of the insulating resin layer, and the width is twice the minimum width of the wiring patterns.