1. A collaborated design management method for supporting a process of determining specifications comprised of design parameters of a product during a design process involving a plurality of design sections or prototyping sections, said method comprising: a first step of inputting into a computer system design parameters of a product-specification draft including at least external dimensions, materials and manufacturing conditions which are input at each design section with constraint conditions for each design parameter related to said product as well as set base data or empirical data for said constraint conditions, rules governing relations among said design parameters and a set of programs necessary for evaluation of said design parameters registered in advance; a second step of autonomously correcting all design parameters or setting all design parameters affected by updating of a design parameter or inputting of a new design parameter; a third step of judging whether values of said corrected design parameters meet said constraint conditions; a fourth step of computing and displaying to a user a difference between a value of a design parameter and a constraint value in the case of a detected constraint violation by said design parameters; a fifth step of requesting the user to correct an inputted value of said design parameter or to modify said constraint condition in the case of the detected constraint violation by said design parameter; a sixth step of creating a list of constraint conditions related to said design parameter which violate said constraint along with set base data of said conditions and displaying said list to the user in case the user has selected an alternative to modify said constraint values; a seventh step of re-cataloging said displayed constraint conditions after being corrected interactively, whereby all relevant design parameters are corrected automatically through collaboration among a plurality of design sections whenever a local design parameter is changed by an individual design section; and constructing the product in accordance with the corrected relevant design parameters.