To ensure that the interests of a wide spectrum of voters are addressed, the Diet is bicameral, with a House of Representatives (lower house) and a House of Councillors (upper house). The membership of both houses consists of lawmakers chosen in national elections in which citizens 20 years old or over participate.

There are 500 seats in the House of Representatives, and 252 in the House of Councillors. Electoral terms are four years for the lower house and six years for the upper house; elections for the latter are held every three years, with half the seats at stake.

Members of the public may stand for election to the House of Representatives if they are 25 or over; the minimum age is 30 for the House of Councillors.

A bill submitted to the Diet by the cabinet or a lawmaker is deliberated separately in the two houses. As a rule, it passes into law after both houses approve it. The Diet also decides on the budget compiled by the cabinet, approves treaties, designates the prime minister, and performs other functions.

If both houses had equal authority, it would be impossible to pass legislation or other measures in the event of disagreement, and the Diet would become paralyzed. The lower house thus has constitutionally guaranteed superiority in certain cases. Specifically, in vital matters like the designation of the prime minister, passage of the budget, and approval of treaties, the lower house's decisions are upheld in case of disagreement. In other legislation, too, the House of Representatives can override an upper house rejection by passing the bill a second time.

Photo courtesy of Ministry of Foreign Affairs.