This research makes use of a cognitive approach to explore a mechanism for associating ideas in a brainstorming session. Firstly, we propose a linking model integrating three principles of idea association (similarity, contrast and contiguity) with two processes of case-based reasoning (retrieval and adaptation). Based on this linking model, an experiment is conducted to elucidate the interactions between ideas and cases, and their mechanisms of retrieval and adaptation. Finally, a framework for case-based reasoning to support idea association called Idea-Maps is proposed, and its mechanism is elucidated.