The terminals that oppose each other when substrates are bonded are designed to be reliably joined. Comprised in a semiconductor device design system are a numerical value acquiring part, which acquires the respective numerical values of a plurality of calculation parameters, a junction estimating part, which, in the case in which a plurality of substrates has been pressed at a prescribed pressure so that the bump front end faces come into contact, estimates whether or not the respective mutually opposing bumps will be joined based on the respective numerical values of the calculation parameters acquired by the numerical value acquiring part, and a change processing part, which, in the case in which it has been estimated by the junction estimating part that any of the bumps will not be joined, gives a warning or performs processing so as to change the numerical value of at least one calculation parameter among the plurality of calculation parameters.