This study has improved the previously proposed models for creation and consensus building processes to propose a process model for cooperative work involving concept sharing. In addition, it has built a system called "MochiFlash" to support the cooperative work process. MochiFlash allows the user to visualize their own concept as an image map through the placement of objects, such as keywords and figures, onto a two-dimensional map. In the cooperative work involving concept sharing with MochiFlash, the users understand each other's concept through communication via their image maps and repeat negotiations among them to reach an agreement. Through a case study using picture book creation as an example, the authors have found that MochiFlash is effective in supporting cooperative work involving concept sharing and that the effective usage pattern depends on the degree of intimacy between the users.