resize iframe alogn with theme design

Hi, I embedded iframe onto my page as responsive design, but embedded contents shows out of theme design when I see the page with smartphone. (with PC, it works well) The page URL is http://dvcon-japan.com/2017/?page_id=351. Could you advise how to fix this issue? I would like to make the iframe resize along with theme design as responsive. I appreciate your help. Thank you, Sumiko