Abstract: Data of an IP module (1) has a hardware part for defining a layout pattern of a first circuit (2) in an integrated circuit and a software part (information described in an HDL or the like) for determining the function of a second circuit (3), and also has connection information for specifying the relation of connecting the first and second circuits. Since a part requiring adjustment such as an interface part takes the form of a software part and has data and the degree of freedom, at the time of designing an integrated circuit, partial modification such as promotion of reduction in power consumption or reduction in chip occupying area in accordance with an external load can be easily made on past design asset data.