Sixty-one percent of unmarried men aged 18 and 34 do not have a partner, nor do half of unmarried women the same age.
The numbers have increased since the previous survey in 2005.
Japan has one of the lowest birth rates in the world – and its population is on course to shrink dramatically by the middle of the century.
So every five years the government carries out a detailed survey of attitudes to sex and marriage.
The latest found that 61% of unmarried men aged 18 to 34 have no girlfriend, and half of women the same age have no boyfriend – a record high.
More than a quarter of the men and 23% of the women said they were not even looking.
Some cited a shortage of money, others a belief that it is impossible to find a good partner once they had passed the age of 25.
Many of the women also said single life suited them better than how they imagined marriage would be.
The survey also found that more than quarter of unmarried men and women between 35 and 39 years old said they had never had sex