Designing a question-answer database is important to make natural conversation for an example-based dialog system. We focused on the method to collect the example sentences by actual conversations with the system. In this study, examples in the database were collected from the conversation logs, then we investigated the relationship between the response accuracy and the number of the interaction. In the experiment, the transcriptions of the user’s utterances are added to the database at every end of the interaction. The responce sentences in the database were created manually. The result showed that the response accuracy appropriateness improved as increasing the number of the interactions and saturated at around 70%. In addition, we compared the collected database with the fully handcrafted database by the subjective evaluation. The score of the user satisfaction, dialog engagement, intelligence, and willingness to use were higher than the handcrafted database, and these results suggested that the proposed method can obtain more appropriate examples to the actual conversation from subjective point of view.