In order to prevent the mistakes at treating soft bag type intravenous solution bags, a certain company performed complete renewal of the display design of fifty-seven kinds of intravenous solution bags based on the human centred design. The requirements towards the display ware specified based on the investigation at several hospitals and manufacture staffs in the company. The design proposal based on the design principles of “exclusivity”, “clearness” and “similarity” was created incorporating with package designer's design know-how. Evaluation experiments and investigation to medical staffs were conducted. Consequently, it was expected that the proposed design will be able to prevent the treatment mistakes, and we can conclude that the design renewal based on the human centred design is useful to reduce medical accidents caused by human error.