The examination of the reason why so narrow minimum width of street as 9 shaku (2.7 m) was legislated by the Urban Building Act in 1919 is the subject of this paper. Throughout long-term preparations of building ordinances in the Meiji era, The minimum standard of street and alley had been intended to legislated separately. The minimum width of "9 shaku" was the final and improved proposal for alley, but in the 1919 Act the difference of street and alley was ignored.