Temporary visitors or people in Japan for less than 1 year

• If you come from a country that signed the Geneva Convention of 1949, you can get an international driving license through your national automobile association (valid 1 year) before going in Japan and drive with it.
  
  
• If you come from France, Germany or Switzerland, your country has not signed the Geneva Convention (but the Vienna one), and you can not use an international driving license in Japan. However, you can use the driving license from your home country, provided that you have a Japanese translation of it (which can be obtained from your country's embassy or consulate in Japan, or from the Japan Automobile Federation).
  
  
• If you come from another country, you will need to get a Japanese driving license in order to drive in Japan.

If you leave from Japan for more than 3 months, you can again use the above-mentioned option for another year.


People in Japan for more than 1 year

To drive in Japan after staying there 1 year, you need to get a Japanese driving license.

• If you have a driving license from one of the countries with which Japan has an agreement, you can get a Japanese license without taking nor written neither practical exam. You just need to go to a license center in your prefecture with your foreign license, an official translation of your license (made by your embassy or the Japan Automobile Federation), take an eye test and prove that you stayed at least three months in the country where your license had been issued before coming to Japan (by showing a diploma, a contract, etc). Those countries are France, Germany, Switzerland, Italy, Belgium, Netherlands, Luxemburg, United Kingdom, Denmark, Ireland, Greece, Spain, Portugal, Sweden, Norway, Iceland, Finland, Australia, New Zealand, Austria and Canada.
  List of the prefectural centers
  
  
• If you have a driving license from another country which has not concluded an agreement with Japan, you will have to take a written (10 questions) and practical exam to obtain a Japanese driving license. This process can be long and expensive... This is typically the case for people with driving licenses from USA, South Korea, Mexico, Taiwan, China, Brazil, Peru, etc.
  

For translation by the Japan Automobile Federation:

Check their updated page for more details; you can also directly check which local offices can translate your driving license, or download the application form and submit it by mail.

It costs 3000 yen per translation, as well as a 290 yen fee for sending zou the document back by mail.