A multilayer resin substrate includes a base material including stacked resin layers including an opening resin layer, a conductor pattern, and an interlayer connection conductor. A concave portion is provided in the base material. The opening resin layer is closer to a first main surface than other resin layers. The concave portion includes a first opening portion provided by a cutting process from one surface of the opening resin layer, and another resin layer. The interlayer connection conductor is provided by filling a conductor in a second opening portion provided by a cutting process from an opposite surface of the opening resin layer. The end portion of the one surface of the first opening portion is not in contact with the conductor pattern.