Some patients with rheumatism cannot use ordinary working chairs, because an ordinary chair cannot accommodate the height requirements for safe and comfortable sitting/standing actions or stability during these actions. We have developed a new functional working chair that assists with standing and sitting for patients with rheumatism, like cooking for instance, allowing them to be supported or take breaks with out experiencing pain. The concept model was first developed in 2003, and then modified and tested to determine the optimum sitting posture for comfort as well as functional performance for patients with rheumatism. These test results were applied to the first prototype. The evaluation of the prototype showed that a patient with rheumatism could sit in the chair securely without pain. By adjusting the cooking and dining tables heights, the person could also cook or eat sitting in this working chair. Now we have developed a second prototype that is commercially available. We review the functions of the newly developed working chair, and the results of the usability assessment by the patients with rheumatism in this paper.