The average Japanese family has ¥16.64 million in savings, more than twice the average annual salary in the nation of 128 million.
2011 saw a 0.4 percent increase from a year earlier, with households of two or more people holding average debt of ¥4.62 million.
Japanese have long enjoyed a reputation as disciplined savers, as rates generally declined in the West in recent decades, including the United States, where economists and politicians have bemoaned low savings rates.
However, the data recently released by the internal affairs ministry also point to a widening savings rate gap, as the nation looks to kick-start its moribund economy and deal with a rapidly aging population, which has put increasing stress on public coffers.
Two-thirds of households saved less than the average ¥16.64 million, the data said, with median savings standing at ¥9.91 million.
Some 10.2 percent of the top-saving families had more than ¥40 million each, while the bottom 11.2 percent had a cushion of less than ¥1 million, the ministry said.