A government survey indicates that the percentage of people 15 and older who have smoked marijuana increased 2.6-fold between 1995 and 2005, although the overall rate remains relatively low.
Cannabis users formed 1.3 percent of all respondents in a 2005 survey on drug use by the National Center of Neurology and Psychiatry, up from 0.5 percent in a previous survey in 1995.
Marijuana finished behind organic solvents, including paint thinner, which at a usage rate of 1.5 percent was the most abused type of drug in Japan.
In both the 1995 and 2005 surveys, the percentage of people who said they have taken stimulant drugs stood at 0.3 percent.
Kiyoshi Wada, who heads the department of drug dependence research at the center's National Institute of Mental Health, called on authorities to work out steps immediately to promote early treatment and social rehabilitation for drug users.
The Tokyo-based national center, an arm of the health ministry, surveyed 5,000 people. Valid responses were received from 3,057 people.
Slightly more than 3 percent of the respondents said they have been offered solvents, while 2.4 percent said they have been offered pot and 1.0 percent stimulant drugs.