This paper proposes to apply Chance Discovery methods to software requirements elicitation. The author’s previous studies indicated that requirements definition work of custom-made type application software had been running through the whole software development process. This trend has been seen among small-scale software development projects, especially for web application system and client/server application system. It is necessary to comprehend that requirements definition work continues through the all software development process. Requirements definition is considered to be knowledge exchange or knowledge share between customer and supplier. Customer can be defined as an expert of the application or an expert of an undeveloped (to be developed in the near future) application system. Supplier can be defined as an expert of IT development. The author believes it might be effective to apply the Knowledge Management process to requirements definition. On the actual situation, there are traditional methods for requirements elicitation that is interaction between customer and supplier, for instance, interviewing to customer, reading the requirements definition from customer and discussing with customer. If applying Knowledge Management methods, it can help that interaction smoothly. On the other hand, it is well known that requirements definition is the principle of the project, however the quality of requirements elicitation much depends on personal factors of each supplier (i.e. project managers, system engineers). Experimentally, skillful project manager or leader knows that sometimes customer has true requirements unconsciously. When true requirements are realized, both customer and supplier will be more satisfied. Therefore, the author believes Chance Discovery methods can contribute to lead the project to be more satisfied and more sophisticated for both customer and supplier exceedingly.