Abstract: A resin-encapsulated semiconductor package and a packaging structure, make it possible to provide for a high density mounting arrangement. Specifically, outer leads protrude from the two long sides of a rectangular package. The inner leads in the package, connected to the outer leads protruding from one long side, are connected through wires to the bonding pads of a semiconductor chip encapsulated in the package, whereas the inner leads in the package, connected to the outer leads protruding from the other long side, are in an electrically floating state in the package. The semiconductor packages are arranged in a direction on a card-shaped mounting board, and the opposed outer leads of adjoining semiconductor packages are electrically connected by wiring on the mounting board. The wirings are laid below the semiconductor packages so that they extend generally linearly.