Search tools for API usage patterns extracted from open-source repositories could provide useful information for application developers. However, API member sets on search results are not necessarily easy to utilize if the results are shown by simple lists because API member sets tend to be similar to each other. We propose a method to improve the searchability of API member sets by utilizing inclusion graphs among API member sets that are automatically extracted from source code. The proposed method incorporates the frequent pattern mining to obtain inclusion graphs and offers the user a way to search API member sets smoothly and intuitively by using a GUI. We describe the details of our method and the design and implementation of the prototype. We discuss the usability of the proposed tool.