Disclosed is a product designing system for designing a given product while setting a design parameter value for each of a plurality of design parameters of the product each contributing to noise and vibration characteristics of an installation base for the product. The system comprises vibration-system setting means for setting a plurality of vibration systems related, respectively, to the noise and vibration characteristics, and formed as at least one vibration system pair inducing a coupled phenomenon that they vibrate while exchanging energy therebetween, coupled-degree calculation means for calculating a coupled degree representing a degree of the coupled phenomenon between respective vibrations in the vibration system pair set by the vibration-system setting means, and design-parameter setting means for setting a plurality of design parameters of the product contributing to the noise and vibration characteristics, and setting a design parameter value for each of the design parameters in such a manner as to reflect the coupled degree calculated by the coupled-degree calculation means thereto.