PURPOSE: To provide an LSI wherein the expansion of a package-mounting area and a large-scale wiring operation are not required in order to mount an external circuit when an internal circuit is changed.

CONSTITUTION: An LSI 100 is provided with the following: an external-circuit mounting region 101 formed on the face of an enclosure faced with an external space when it is mounted; and external terminals 102 which are installed inside the external-circuit mounting region 101 and which are connected to an internal circuit for the LSI. An external integrated circuit 103 as an external circuit mounted on the LSI 100 or an external memory 104 is provided with terminals which are brought into contact with and connected to the external terminals 102 when it is mounted on the VLSI 100; the terminals are connected to a required internal circuit for the external circuit.