Debate about the document, which was drafted by the United States and its allies after Japan's surrender in World War II, has intensified since Japanese Prime Minister Shinzo Abe indicated he planned to push for changes, The Japan Times reported Friday.
Thousands of people who support the current document carried out a protest March in Tokyo, while about 450 people attended an annual gathering of Abe's Liberal Democratic Party.
Recent polls have suggested the majority of Japanese support revision, said Junpei Kiyohara, a representative of an organization that favors constitutional changes.
One provision being targeted prevents Japan from going to war, a provision Kiyohara says has resulted in pressure by China on Japan's sovereignty as exemplified by the dispute over the Senkau Islands.
Changes must also be made, he said, to a section that requires constitutional amendments be approved by a two-thirds majority on both houses of Parliament and then voted on by the public.
Opponents of the constitution changes say Abe's intention is to make it possible for Japan to engage in war.