The objective of this research was to investigate the causal factor of inhabitant migration of Toba Bataknese ethnic which come from North Tapanuli (North Sumatera) years 1965-1975 to the East Bandarjaya Terbanggi Besar Subdistrict in Middle Lampung Regency. The method that was used in this research was descriptive method. The population in this research was the whole citizen of East Bandarjaya which come from Toba Bataknese Ethnic who did the migration from North Tapanuli (North Sumatera) years 1965-1975 that was 33 patriarch. The data collecting techniques that were used were interview, documentation, observation, whereas the data analysis technique used analysis technique of qualitative data in the form of percentage. The result of the research showed that there were some causal factors of Toba Bataknese ethnic in doing the migration in years 1965-1975 to the East Bandarjaya , they were, kind of job in the origin area that was 84.85%, the income that was got there was 84.85%, go abroad tradition of Toba Bataknese Ethnic was 93.4%, and relative or friend information was 69.70%. The culture factor that was go abroad tradition became the most influential in this research. Another factor that got the lowest answer was individual factor, it was relative or friend information