This paper reports what issues in the whole of requirements engineering processes ChatGPT can address, considering the characteristics of large language models (LLMs) used in ChatGPT. Through a simple case study of Library System, we discuss how ChatGPT can assist both stakeholders and requirements analysts well in each step of a requirements engineering process such as requirements elicitation, documentation, validation and management. The responses of ChatGPT to instructed tasks are evaluated, albeit subjectively from our views such as their suitability and usefulness. In addition, we also focus on prompts, which are input texts that instruct ChatGPT to generate responses and to perform tasks, for each step of the process. Furthermore, to make ChatGPT’s assistance more powerful and suitable, we discuss the future research plan.