We propose a new requirements elicitation method in such a domain of ERP, CRM, and SCM by using specifications of several existing package software. We have analyzed the requirements elicitation processes of experienced analysts in a specific domain, and found that they clarify requirements by referring the specifications of existing packages that seem to be satisfied with customer's needs. This process can be formulated into two sub-processes: 1) package selection, where an analyst compares the customer's needs with functions/non-functions of packages and selects the suitable candidates of packages; and 2) requirements evolution, where he examines the selected packages with his customer and an approved part of specifications of packages are added into their requirements. The proposed method, called PAORE (PAckage Oriented Requirements Elicitation method) is designed based on the analysis. We applied this method to a simple but realistic example of Web-based Sales Supporting System and assessed it.