An extensible and contractible mounting board that includes an extensible and contractible substrate; an extensible and contractible wiring line on one main surface of the extensible and contractible substrate; an electronic component electrically connected to the extensible and contractible wiring line; and a resin portion in contact with the extensible and contractible wiring line and overlapping an end portion of a connection region between the extensible and contractible wiring line and the electronic component in a plan view of the extensible and contractible mounting board, the resin portion having a cutout portion that overlaps the extensible and contractible wiring line. A Young's modulus of the resin portion is higher than a Young's modulus of the extensible and contractible substrate.