Volcano monitoring and the research have been improved significantly in Japan since 1974, when the national program for prediction of volcanic eruption started. Efforts to collect high-quality data of ground-deformation, geomagnetic and other geophysical observations as well as seismic observation have been done, and precursory phenomena of magmatic eruptions have been observed at several volcanoes. In this paer, recent progresses in geophysical study on eruption mechanism, monitoring methods and magma supply system were summarized, and the results were evaluated.