A resin substrate includes a first portion including a plurality of resin sheets provided at one end in a stacking direction and a second portion including a plurality of resin sheets provided at the other end in the stacking direction. The thickness of the plurality of resin sheets is the same or substantially the same as the thickness of the first portion and the second portion. The density of planar conductor patterns of the first portion with respect to the volume of the first portion is lower than the density of planar conductor patterns of the second portion with respect to the volume of the second portion. The average of the diameters of the first interlayer connection conductor provided in the first portion is greater than the average of the diameters of the second interlayer connection conductor provided in the second portion.