More than 60% of cancer patients obtain cancer information from the Internet. However, on the Internet of Japan, there are many inappropriate information about cancer including advertisements for commercial purposes. In search sites, strong Search Engine Optimization are applied, paid advertisements are given priority, and it is difficult for patients without certain medical knowledge to judge whether information is accurate, and patients and families do not receive standard treatment. There is a problem that it is induced to wrong cancer treatment. In order to solve this problem, we believe that multifaceted response in addition to promoting the establishment of a system for creating information by collaboration among medical staff across organizations, promotion of communication between medical professionals and patients, regulation of Internet advertisements of medical institutions by medical law, improvement of the search algorithm on the search site, and improvement of information literacy of the patient are necessary.