Naha city has two urban retail core areas: Kokusai Street and Naha Shintoshin area. Kokusai Street is a typical traditional shopping street, which includes two department stores, some shopping centers, and traditional markets. Naha Shintoshin is a newly developed shopping area which includes two shopping centers; one is an open mall shopping center, “Ameku Riubou Rakuichi” opened in 2001 and the other a shopping center with a cinema complex, “Naha Mainplace” opened in 2002. Now on August 10, 2003, a new monorail line was opened, which interlinks above two retail core areas and the Naha airport. The new monorail line, which was the first railroad line introduced in Okinawa since the aftermath of World War II, was welcomed by many local people to expect the decrease of traffic congestion at the midtown area, the increase of customers visiting above two retail areas and so and so forth. This paper aims to forecast the impacts of the new monorail line on the two retail core areas in Naha City from the viewpoint of customer shopping behavior. For the purpose, we conducted an on-site small consumer behavior survey on July 12-13 before the new monorail line started running. For this survey, we selected three sampling sites; two from Kokusai Street and one from Shintoshin, and the respondents were randomly chosen from the visitors at these sampling sites. In the questionnaire, the respondents were asked how they would change the numbers of visits to the two retail core areas after the new monorail was setup and how they actually had changed the number of visits to Kokusai Street after the establishment of Shintoshin. From responses to these questionnaire items, we found that while the development of Shintoshin had not much effect on the number of visits to Kokusai Street, the introduction of the monorail is likely to have much more effect on Kokusai Street. First, the respondents who live near monorail stations would increase the number of visits to both Kokusai Street and Shintoshin than those who live far away from the stations. Second, the respondents near monorail stations would increase the number of visits to Shintoshin more than to Kokusai Street. Third, this inclination becomes much stronger for bus users since almost all of the bus users near monorail stations would increase the visits to Shintoshin while only half of them would increase the visits to Kokusai Street.