As the propagation of smart devices has increased and the variety of the devices also has been diversified, various existing functions are concentrated on these smart devices. One of the phenomena is that the paper-book market has partially transferred into an e-Book market. As the demand of the e-Book has increased over time, the improvement of the types of e-Book on the market can be observed. In this study, the usability evaluation on the interface of the e-Book viewer for the types of application, which can be installed in the smart devices, has been conducted. The items for the usability evaluation of the e-Book were defined, the usage patterns were observed objectively and a questionnaire technique was applied. By analyzing the usability evaluation of e-Book interface, the directions for production and improvement of e-Books have been suggested.