The purpose of the present study is to figure out what the issues faced by architecture were at the time immediately before the transition to modern era centering of the works of Otto Wagner who acted in Vienna, Austria at the Fin de siècle. Therefore, the following points were examined in the present study; first, how were new spaces necessary to accommodate modern lives organized and how were the plans changed; second, how did the external expressions of architecture pursued by Otto Wagner appeared between arts and technologies, between historicism and modernity, and between decorations and functions. Through the study, it could be seen that Wagner began from historicism and traditionalism and tried to compromise them with modernity. Many modern characteristics appeared a priori in Wagner’s works from the construction of ‘Linke Wien Zeile housing block’ in 1898, his works completely broke from the typical historicism styles to open the period of inventive ‘Secession styles.’ At that time, Wagner concentrated on so called ‘flat decorations.’ Thereafter, his residential architecture completed to modern styles with ‘Neustiftgasse housing block’ as the peak. The characteristics of modern housing as above became a cornerstone of the modern functionalism later.