A government white paper published on Tuesday, showed that number, equal to the total population of Portugal, was up 510,000 from the previous year at 10,040,000 people.
The paper said the number of people aged 65 or older stood at 23.63 million, or 18.5 percent of the total population, as of October 1 last year, up from 18 percent the year before.
Japan has the world's highest life expectancy, at 78.07 years for men and 84.93 for women, and the number of centenarians also hit a record high of 17,934 in 2002.
The world's oldest woman and man, Kamato Hongo, 115, and Yukichi Chuganji, 114, both live on the southern Japan island of Kyushu.
According to some estimates, Japan will have roughly one person over 65 for every two of working age by 2025, a higher dependency ratio than any other major industrialised nation.
The rapid ageing of society, and tumbling birthrates, have raised concerns that pension obligations may become unmanageable.