A resin multilayer substrate includes a first resin layer including a thermoplastic resin as a main material, a second resin layer including the thermoplastic resin as a main material and superposed on the first resin layer, a first interlayer-connection conductor passing through the first resin layer in a thickness direction, and a first conductor pattern at an area including a region in which the first interlayer-connection conductor is exposed at the surface of the first resin layer between the first resin layer and the second resin layer. The first conductor pattern includes a portion in or at which a portion of the first interlayer-connection conductor is disposed. The first conductor pattern includes a first portion covering the region exposed at the surface of the first resin layer; and a second portion disposed surrounding the first portion. The first portion and the second portion have different thicknesses from each other.