The objective of upgrade design is to extend product life so as to reduce consumption volume of resources and energy usage. However, difficulty of upgrade design resides within prediction of future trend such as technological trends and market trends, and upgrade design should be robusts against uncertainty of future predection. This paper proposes a design methodology for upgradable products, and illustrates a prototype upgrade design support tool which can handle changes of user requirement and market trend. With a design example of a vacuume cleaner, this papar also demonstrates the features of the upgrade design tool.