Following recent advances in robotics for supporting human activities, ethical reviews similar to those for medical research and development have been requested for clinical trials in the development process of this field of robotics. In this environment, many robot developers have found it difficult to understand the criteria for these ethical reviews. One of the basic reasons for this difficulty is the methodology in robotics. That is, trials are characterized as exploratory rather than confirmatory during the development process. However, to make trials scientifically sound and ethically acceptable, it is important to plan serial trials so that their objectives gradually shift from exploration to confirmation. To address this problem, we propose a development process for human assistive robots. This process is intended to be a reference for developers planning experimental protocols for planning clinical trials and forms a basis for guidelines on the development of human assistive robots.