Mount Oyama on Miyake Island and Mount Usu in Hokkaido were among six volcanoes that erupted last year in Japan, the Meteorological Agency said.
The six also include Mount Suribachi on Iwojima in the Ogasawara island chain and volcanoes on three islands, the agency said Tuesday.
Meanwhile, 21 volcanoes, including Mount Fuji, showed signs of activity, including gas eruptions and volcanic quakes.
The data are nearly identical to the figures in 2000, when six volcanoes erupted and 22 others showed activity, it said.
However, the data exceeded the average level of volcano activity between 1990 and 1999, during which 4.2 mountains erupted and 14.9 showed signs of activity.
Small-scale eruptions were observed on Miyake Island 17 times last year, and its output of sulfur dioxide, a volcanic gas, is estimated to have totaled 8.2 million tons, it said.
Volcanic activity on Mount Usu has tapered off, with no volcanic smoke observed in its northwestern crater since the end of last month.
Low-frequency quakes occurred 132 times on Mount Fuji in April and 163 times in May, though in later months they tapered off.
Miyake Island was completely evacuated in September 2000 due to strong volcanic activity, and it is unclear when the island will be safe for human habitation.