Population density from the population census conducted in 2005. Population density is calculated by dividing population by area. However, as indicated in Area, the areas of each prefecture are undefined due to undefined areas such as lakes on prefectural borders. Therefore, in the population census, population density is calculated based on the Ministry of Internal Affairs and Communication Statistics Bureau's estimated areas with respect to undefined areas.

The population density is greatest in Tokyo, with 343 people/km2. Tokyo is followed by Osaka, Kanagawa, Saitama and Aichi. On the other hand, the population density is smallest in Hokkaido with only 72 people/km2. Hokkaido is followed by Iwate, Akita, Shimane and Kochi.

The correlative ranking shows that it is highly correlated with the average price of residential land, numerically verifying that the price of land is high in heavily populated areas. It is also positvely correlated with Railway Passenger Transport and negatively correlated with Automobiles Registered and Homeownership, from which it can be seen that in densely populated areas, many people live in rented accomodation and move by train rather than by car.