A multilayer resin substrate includes a stacked body including resin layers stacked on each other, a first planar conductor on a resin layer, and an interlayer connection conductor on a resin layer. The interlayer connection conductor includes a first interlayer connection conductor connected to an external conductor, and a second interlayer connection conductor bonded to the first interlayer connection conductor and a planar conductor. The first and second interlayer connection conductors are made of different materials. The second interlayer connection conductor includes a constricted portion including a smaller planar cross-sectional area than a different portion, between a bonding portion to which the first interlayer connection conductor is bonded and a bonding portion to which the planar conductor is bonded.