A software building support system capable of efficiently building, managing and reusing a software program. The software building support system includes a program design part for supporting the design of a composite program and for outputting the results thereof as a program structure information. The program design part includes a component line-connection part for defining the structure of the composite program on the basis of instructions obtained by a graphical interface, and a composite component setting part for setting a plurality of software components as a single composite component. The composite component setting part includes a terminal setting part for setting a terminal of the composite component, which is used for allowing the composite component to communicate with another external component, and an attribute setting part for setting an inherent property of the composite component.