Data science can be applied to each of the three fields of medicine: basic, clinical, and social. In basic medicine research, data science is used for many applications, such as genomic analysis. In clinical medicine, which is about caring for the medical needs of patients, data science is also employed, such as in the use of AI in image diagnosis. In this lecture, I will focus on social medicine, especially on Health Service Research (HSR). In order to realize high-quality health services, we need to take a longitudinal point of view – examining health behavior in daily life, access to clinics and hospitals, and medical treatment. Further, we need to investigate how health services are operating at the community level, including long-term care and, at the same time, it is necessary to a broad perspective of how each medical or long-term care services is provided. To get such a big perspective, we need access to big data. In this lecture, I will also touch on epidemiology and statistics, which are the foundation of social medicine, and explain the way of thinking for approaching data science. I will also address the current state of big data on medical and long-term care in Japan.