This is a short perspective paper discussing the potential use of machine learning for scientific discovery. Optimizing and streamlining the development of scientific knowledge is a critical issue for the future of humanity. In recent years, machine learning have begun to accelerate scientific progress. However, many of them have been about automation specific to individual scientific domains. In this paper, we emphasize the importance of discussing how to apply machine learning to more general scientific processes as well. We then briefly discuss some possible future research directions to automate scientific discovery by machine learning.